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Linus Torvalds1da177e2005-04-16 15:20:36 -07001
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002 Linux Ethernet Bonding Driver HOWTO
3
Jay Vosburgh9a6c6862007-11-13 20:25:48 -08004 Latest update: 12 November 2007
Linus Torvalds1da177e2005-04-16 15:20:36 -07005
6Initial release : Thomas Davis <tadavis at lbl.gov>
7Corrections, HA extensions : 2000/10/03-15 :
8 - Willy Tarreau <willy at meta-x.org>
9 - Constantine Gavrilov <const-g at xpert.com>
10 - Chad N. Tindel <ctindel at ieee dot org>
11 - Janice Girouard <girouard at us dot ibm dot com>
12 - Jay Vosburgh <fubar at us dot ibm dot com>
13
14Reorganized and updated Feb 2005 by Jay Vosburgh
Auke Kok6224e012006-06-08 11:15:35 -070015Added Sysfs information: 2006/04/24
16 - Mitch Williams <mitch.a.williams at intel.com>
Linus Torvalds1da177e2005-04-16 15:20:36 -070017
Jay Vosburgh00354cf2005-07-21 12:18:02 -070018Introduction
19============
Linus Torvalds1da177e2005-04-16 15:20:36 -070020
Jay Vosburgh00354cf2005-07-21 12:18:02 -070021 The Linux bonding driver provides a method for aggregating
22multiple network interfaces into a single logical "bonded" interface.
23The behavior of the bonded interfaces depends upon the mode; generally
24speaking, modes provide either hot standby or load balancing services.
25Additionally, link integrity monitoring may be performed.
26
27 The bonding driver originally came from Donald Becker's
28beowulf patches for kernel 2.0. It has changed quite a bit since, and
29the original tools from extreme-linux and beowulf sites will not work
30with this version of the driver.
31
32 For new versions of the driver, updated userspace tools, and
33who to ask for help, please follow the links at the end of this file.
Linus Torvalds1da177e2005-04-16 15:20:36 -070034
35Table of Contents
36=================
37
381. Bonding Driver Installation
39
402. Bonding Driver Options
41
423. Configuring Bonding Devices
Auke Kok6224e012006-06-08 11:15:35 -0700433.1 Configuration with Sysconfig Support
443.1.1 Using DHCP with Sysconfig
453.1.2 Configuring Multiple Bonds with Sysconfig
463.2 Configuration with Initscripts Support
473.2.1 Using DHCP with Initscripts
483.2.2 Configuring Multiple Bonds with Initscripts
493.3 Configuring Bonding Manually with Ifenslave
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700503.3.1 Configuring Multiple Bonds Manually
Auke Kok6224e012006-06-08 11:15:35 -0700513.4 Configuring Bonding Manually via Sysfs
Linus Torvalds1da177e2005-04-16 15:20:36 -070052
Auke Kok6224e012006-06-08 11:15:35 -0700534. Querying Bonding Configuration
544.1 Bonding Configuration
554.2 Network Configuration
Linus Torvalds1da177e2005-04-16 15:20:36 -070056
Auke Kok6224e012006-06-08 11:15:35 -0700575. Switch Configuration
Linus Torvalds1da177e2005-04-16 15:20:36 -070058
Auke Kok6224e012006-06-08 11:15:35 -0700596. 802.1q VLAN Support
Linus Torvalds1da177e2005-04-16 15:20:36 -070060
Auke Kok6224e012006-06-08 11:15:35 -0700617. Link Monitoring
627.1 ARP Monitor Operation
637.2 Configuring Multiple ARP Targets
647.3 MII Monitor Operation
Linus Torvalds1da177e2005-04-16 15:20:36 -070065
Auke Kok6224e012006-06-08 11:15:35 -0700668. Potential Trouble Sources
678.1 Adventures in Routing
688.2 Ethernet Device Renaming
698.3 Painfully Slow Or No Failed Link Detection By Miimon
Linus Torvalds1da177e2005-04-16 15:20:36 -070070
Auke Kok6224e012006-06-08 11:15:35 -0700719. SNMP agents
Linus Torvalds1da177e2005-04-16 15:20:36 -070072
Auke Kok6224e012006-06-08 11:15:35 -07007310. Promiscuous mode
Linus Torvalds1da177e2005-04-16 15:20:36 -070074
Auke Kok6224e012006-06-08 11:15:35 -07007511. Configuring Bonding for High Availability
7611.1 High Availability in a Single Switch Topology
7711.2 High Availability in a Multiple Switch Topology
7811.2.1 HA Bonding Mode Selection for Multiple Switch Topology
7911.2.2 HA Link Monitoring for Multiple Switch Topology
Linus Torvalds1da177e2005-04-16 15:20:36 -070080
Auke Kok6224e012006-06-08 11:15:35 -07008112. Configuring Bonding for Maximum Throughput
8212.1 Maximum Throughput in a Single Switch Topology
8312.1.1 MT Bonding Mode Selection for Single Switch Topology
8412.1.2 MT Link Monitoring for Single Switch Topology
8512.2 Maximum Throughput in a Multiple Switch Topology
8612.2.1 MT Bonding Mode Selection for Multiple Switch Topology
8712.2.2 MT Link Monitoring for Multiple Switch Topology
Linus Torvalds1da177e2005-04-16 15:20:36 -070088
Auke Kok6224e012006-06-08 11:15:35 -07008913. Switch Behavior Issues
9013.1 Link Establishment and Failover Delays
9113.2 Duplicated Incoming Packets
Linus Torvalds1da177e2005-04-16 15:20:36 -070092
Auke Kok6224e012006-06-08 11:15:35 -07009314. Hardware Specific Considerations
9414.1 IBM BladeCenter
Jay Vosburgh00354cf2005-07-21 12:18:02 -070095
Auke Kok6224e012006-06-08 11:15:35 -07009615. Frequently Asked Questions
Jay Vosburgh00354cf2005-07-21 12:18:02 -070097
Auke Kok6224e012006-06-08 11:15:35 -07009816. Resources and Links
Linus Torvalds1da177e2005-04-16 15:20:36 -070099
100
1011. Bonding Driver Installation
102==============================
103
104 Most popular distro kernels ship with the bonding driver
105already available as a module and the ifenslave user level control
106program installed and ready for use. If your distro does not, or you
107have need to compile bonding from source (e.g., configuring and
108installing a mainline kernel from kernel.org), you'll need to perform
109the following steps:
110
1111.1 Configure and build the kernel with bonding
112-----------------------------------------------
113
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700114 The current version of the bonding driver is available in the
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115drivers/net/bonding subdirectory of the most recent kernel source
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700116(which is available on http://kernel.org). Most users "rolling their
117own" will want to use the most recent kernel from kernel.org.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118
119 Configure kernel with "make menuconfig" (or "make xconfig" or
120"make config"), then select "Bonding driver support" in the "Network
121device support" section. It is recommended that you configure the
122driver as module since it is currently the only way to pass parameters
123to the driver or configure more than one bonding device.
124
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700125 Build and install the new kernel and modules, then continue
126below to install ifenslave.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127
1281.2 Install ifenslave Control Utility
129-------------------------------------
130
131 The ifenslave user level control program is included in the
132kernel source tree, in the file Documentation/networking/ifenslave.c.
133It is generally recommended that you use the ifenslave that
134corresponds to the kernel that you are using (either from the same
135source tree or supplied with the distro), however, ifenslave
136executables from older kernels should function (but features newer
137than the ifenslave release are not supported). Running an ifenslave
138that is newer than the kernel is not supported, and may or may not
139work.
140
141 To install ifenslave, do the following:
142
143# gcc -Wall -O -I/usr/src/linux/include ifenslave.c -o ifenslave
144# cp ifenslave /sbin/ifenslave
145
146 If your kernel source is not in "/usr/src/linux," then replace
147"/usr/src/linux/include" in the above with the location of your kernel
148source include directory.
149
150 You may wish to back up any existing /sbin/ifenslave, or, for
151testing or informal use, tag the ifenslave to the kernel version
152(e.g., name the ifenslave executable /sbin/ifenslave-2.6.10).
153
154IMPORTANT NOTE:
155
156 If you omit the "-I" or specify an incorrect directory, you
157may end up with an ifenslave that is incompatible with the kernel
158you're trying to build it for. Some distros (e.g., Red Hat from 7.1
159onwards) do not have /usr/include/linux symbolically linked to the
160default kernel source include directory.
161
Auke Kok6224e012006-06-08 11:15:35 -0700162SECOND IMPORTANT NOTE:
163 If you plan to configure bonding using sysfs, you do not need
164to use ifenslave.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165
1662. Bonding Driver Options
167=========================
168
Jay Vosburgh9a6c6862007-11-13 20:25:48 -0800169 Options for the bonding driver are supplied as parameters to the
170bonding module at load time, or are specified via sysfs.
171
172 Module options may be given as command line arguments to the
173insmod or modprobe command, but are usually specified in either the
174/etc/modules.conf or /etc/modprobe.conf configuration file, or in a
175distro-specific configuration file (some of which are detailed in the next
176section).
177
178 Details on bonding support for sysfs is provided in the
179"Configuring Bonding Manually via Sysfs" section, below.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180
181 The available bonding driver parameters are listed below. If a
182parameter is not specified the default value is used. When initially
183configuring a bond, it is recommended "tail -f /var/log/messages" be
184run in a separate window to watch for bonding driver error messages.
185
186 It is critical that either the miimon or arp_interval and
187arp_ip_target parameters be specified, otherwise serious network
188degradation will occur during link failures. Very few devices do not
189support at least miimon, so there is really no reason not to use it.
190
191 Options with textual values will accept either the text name
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700192or, for backwards compatibility, the option value. E.g.,
193"mode=802.3ad" and "mode=4" set the same mode.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194
195 The parameters are as follows:
196
Jay Vosburghfd989c82008-11-04 17:51:16 -0800197ad_select
198
199 Specifies the 802.3ad aggregation selection logic to use. The
200 possible values and their effects are:
201
202 stable or 0
203
204 The active aggregator is chosen by largest aggregate
205 bandwidth.
206
207 Reselection of the active aggregator occurs only when all
208 slaves of the active aggregator are down or the active
209 aggregator has no slaves.
210
211 This is the default value.
212
213 bandwidth or 1
214
215 The active aggregator is chosen by largest aggregate
216 bandwidth. Reselection occurs if:
217
218 - A slave is added to or removed from the bond
219
220 - Any slave's link state changes
221
222 - Any slave's 802.3ad association state changes
223
224 - The bond's adminstrative state changes to up
225
226 count or 2
227
228 The active aggregator is chosen by the largest number of
229 ports (slaves). Reselection occurs as described under the
230 "bandwidth" setting, above.
231
232 The bandwidth and count selection policies permit failover of
233 802.3ad aggregations when partial failure of the active aggregator
234 occurs. This keeps the aggregator with the highest availability
235 (either in bandwidth or in number of ports) active at all times.
236
237 This option was added in bonding version 3.4.0.
238
Linus Torvalds1da177e2005-04-16 15:20:36 -0700239arp_interval
240
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700241 Specifies the ARP link monitoring frequency in milliseconds.
Jay Vosburghf5b2b962006-09-22 21:54:53 -0700242
243 The ARP monitor works by periodically checking the slave
244 devices to determine whether they have sent or received
245 traffic recently (the precise criteria depends upon the
246 bonding mode, and the state of the slave). Regular traffic is
247 generated via ARP probes issued for the addresses specified by
248 the arp_ip_target option.
249
250 This behavior can be modified by the arp_validate option,
251 below.
252
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700253 If ARP monitoring is used in an etherchannel compatible mode
254 (modes 0 and 2), the switch should be configured in a mode
255 that evenly distributes packets across all links. If the
256 switch is configured to distribute the packets in an XOR
Linus Torvalds1da177e2005-04-16 15:20:36 -0700257 fashion, all replies from the ARP targets will be received on
258 the same link which could cause the other team members to
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700259 fail. ARP monitoring should not be used in conjunction with
260 miimon. A value of 0 disables ARP monitoring. The default
Linus Torvalds1da177e2005-04-16 15:20:36 -0700261 value is 0.
262
263arp_ip_target
264
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700265 Specifies the IP addresses to use as ARP monitoring peers when
266 arp_interval is > 0. These are the targets of the ARP request
267 sent to determine the health of the link to the targets.
268 Specify these values in ddd.ddd.ddd.ddd format. Multiple IP
269 addresses must be separated by a comma. At least one IP
270 address must be given for ARP monitoring to function. The
271 maximum number of targets that can be specified is 16. The
272 default value is no IP addresses.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700273
Jay Vosburghf5b2b962006-09-22 21:54:53 -0700274arp_validate
275
276 Specifies whether or not ARP probes and replies should be
277 validated in the active-backup mode. This causes the ARP
278 monitor to examine the incoming ARP requests and replies, and
279 only consider a slave to be up if it is receiving the
280 appropriate ARP traffic.
281
282 Possible values are:
283
284 none or 0
285
286 No validation is performed. This is the default.
287
288 active or 1
289
290 Validation is performed only for the active slave.
291
292 backup or 2
293
294 Validation is performed only for backup slaves.
295
296 all or 3
297
298 Validation is performed for all slaves.
299
300 For the active slave, the validation checks ARP replies to
301 confirm that they were generated by an arp_ip_target. Since
302 backup slaves do not typically receive these replies, the
303 validation performed for backup slaves is on the ARP request
304 sent out via the active slave. It is possible that some
305 switch or network configurations may result in situations
306 wherein the backup slaves do not receive the ARP requests; in
307 such a situation, validation of backup slaves must be
308 disabled.
309
310 This option is useful in network configurations in which
311 multiple bonding hosts are concurrently issuing ARPs to one or
312 more targets beyond a common switch. Should the link between
313 the switch and target fail (but not the switch itself), the
314 probe traffic generated by the multiple bonding instances will
315 fool the standard ARP monitor into considering the links as
316 still up. Use of the arp_validate option can resolve this, as
317 the ARP monitor will only consider ARP requests and replies
318 associated with its own instance of bonding.
319
320 This option was added in bonding version 3.1.0.
321
Linus Torvalds1da177e2005-04-16 15:20:36 -0700322downdelay
323
324 Specifies the time, in milliseconds, to wait before disabling
325 a slave after a link failure has been detected. This option
326 is only valid for the miimon link monitor. The downdelay
327 value should be a multiple of the miimon value; if not, it
328 will be rounded down to the nearest multiple. The default
329 value is 0.
330
Jay Vosburghdd957c52007-10-09 19:57:24 -0700331fail_over_mac
332
333 Specifies whether active-backup mode should set all slaves to
Jay Vosburgh3915c1e82008-05-17 21:10:14 -0700334 the same MAC address at enslavement (the traditional
335 behavior), or, when enabled, perform special handling of the
336 bond's MAC address in accordance with the selected policy.
Jay Vosburghdd957c52007-10-09 19:57:24 -0700337
Jay Vosburgh3915c1e82008-05-17 21:10:14 -0700338 Possible values are:
Jay Vosburghdd957c52007-10-09 19:57:24 -0700339
Jay Vosburgh3915c1e82008-05-17 21:10:14 -0700340 none or 0
Jay Vosburghdd957c52007-10-09 19:57:24 -0700341
Jay Vosburgh3915c1e82008-05-17 21:10:14 -0700342 This setting disables fail_over_mac, and causes
343 bonding to set all slaves of an active-backup bond to
344 the same MAC address at enslavement time. This is the
345 default.
Jay Vosburghdd957c52007-10-09 19:57:24 -0700346
Jay Vosburgh3915c1e82008-05-17 21:10:14 -0700347 active or 1
Jay Vosburghdd957c52007-10-09 19:57:24 -0700348
Jay Vosburgh3915c1e82008-05-17 21:10:14 -0700349 The "active" fail_over_mac policy indicates that the
350 MAC address of the bond should always be the MAC
351 address of the currently active slave. The MAC
352 address of the slaves is not changed; instead, the MAC
353 address of the bond changes during a failover.
354
355 This policy is useful for devices that cannot ever
356 alter their MAC address, or for devices that refuse
357 incoming broadcasts with their own source MAC (which
358 interferes with the ARP monitor).
359
360 The down side of this policy is that every device on
361 the network must be updated via gratuitous ARP,
362 vs. just updating a switch or set of switches (which
363 often takes place for any traffic, not just ARP
364 traffic, if the switch snoops incoming traffic to
365 update its tables) for the traditional method. If the
366 gratuitous ARP is lost, communication may be
367 disrupted.
368
369 When this policy is used in conjuction with the mii
370 monitor, devices which assert link up prior to being
371 able to actually transmit and receive are particularly
372 susecptible to loss of the gratuitous ARP, and an
373 appropriate updelay setting may be required.
374
375 follow or 2
376
377 The "follow" fail_over_mac policy causes the MAC
378 address of the bond to be selected normally (normally
379 the MAC address of the first slave added to the bond).
380 However, the second and subsequent slaves are not set
381 to this MAC address while they are in a backup role; a
382 slave is programmed with the bond's MAC address at
383 failover time (and the formerly active slave receives
384 the newly active slave's MAC address).
385
386 This policy is useful for multiport devices that
387 either become confused or incur a performance penalty
388 when multiple ports are programmed with the same MAC
389 address.
390
391
392 The default policy is none, unless the first slave cannot
393 change its MAC address, in which case the active policy is
394 selected by default.
395
396 This option may be modified via sysfs only when no slaves are
397 present in the bond.
398
399 This option was added in bonding version 3.2.0. The "follow"
400 policy was added in bonding version 3.3.0.
Jay Vosburghdd957c52007-10-09 19:57:24 -0700401
Linus Torvalds1da177e2005-04-16 15:20:36 -0700402lacp_rate
403
404 Option specifying the rate in which we'll ask our link partner
405 to transmit LACPDU packets in 802.3ad mode. Possible values
406 are:
407
408 slow or 0
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700409 Request partner to transmit LACPDUs every 30 seconds
Linus Torvalds1da177e2005-04-16 15:20:36 -0700410
411 fast or 1
412 Request partner to transmit LACPDUs every 1 second
413
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700414 The default is slow.
415
Linus Torvalds1da177e2005-04-16 15:20:36 -0700416max_bonds
417
418 Specifies the number of bonding devices to create for this
419 instance of the bonding driver. E.g., if max_bonds is 3, and
420 the bonding driver is not already loaded, then bond0, bond1
Jay Vosburghb8a97872008-06-13 18:12:04 -0700421 and bond2 will be created. The default value is 1. Specifying
422 a value of 0 will load bonding, but will not create any devices.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700423
424miimon
425
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700426 Specifies the MII link monitoring frequency in milliseconds.
427 This determines how often the link state of each slave is
428 inspected for link failures. A value of zero disables MII
429 link monitoring. A value of 100 is a good starting point.
430 The use_carrier option, below, affects how the link state is
Linus Torvalds1da177e2005-04-16 15:20:36 -0700431 determined. See the High Availability section for additional
432 information. The default value is 0.
433
434mode
435
436 Specifies one of the bonding policies. The default is
437 balance-rr (round robin). Possible values are:
438
439 balance-rr or 0
440
441 Round-robin policy: Transmit packets in sequential
442 order from the first available slave through the
443 last. This mode provides load balancing and fault
444 tolerance.
445
446 active-backup or 1
447
448 Active-backup policy: Only one slave in the bond is
449 active. A different slave becomes active if, and only
450 if, the active slave fails. The bond's MAC address is
451 externally visible on only one port (network adapter)
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700452 to avoid confusing the switch.
453
454 In bonding version 2.6.2 or later, when a failover
455 occurs in active-backup mode, bonding will issue one
456 or more gratuitous ARPs on the newly active slave.
Auke Kok6224e012006-06-08 11:15:35 -0700457 One gratuitous ARP is issued for the bonding master
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700458 interface and each VLAN interfaces configured above
459 it, provided that the interface has at least one IP
460 address configured. Gratuitous ARPs issued for VLAN
461 interfaces are tagged with the appropriate VLAN id.
462
463 This mode provides fault tolerance. The primary
464 option, documented below, affects the behavior of this
465 mode.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700466
467 balance-xor or 2
468
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700469 XOR policy: Transmit based on the selected transmit
470 hash policy. The default policy is a simple [(source
471 MAC address XOR'd with destination MAC address) modulo
472 slave count]. Alternate transmit policies may be
473 selected via the xmit_hash_policy option, described
474 below.
475
476 This mode provides load balancing and fault tolerance.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700477
478 broadcast or 3
479
480 Broadcast policy: transmits everything on all slave
481 interfaces. This mode provides fault tolerance.
482
483 802.3ad or 4
484
485 IEEE 802.3ad Dynamic link aggregation. Creates
486 aggregation groups that share the same speed and
487 duplex settings. Utilizes all slaves in the active
488 aggregator according to the 802.3ad specification.
489
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700490 Slave selection for outgoing traffic is done according
491 to the transmit hash policy, which may be changed from
492 the default simple XOR policy via the xmit_hash_policy
493 option, documented below. Note that not all transmit
494 policies may be 802.3ad compliant, particularly in
495 regards to the packet mis-ordering requirements of
496 section 43.2.4 of the 802.3ad standard. Differing
497 peer implementations will have varying tolerances for
498 noncompliance.
499
500 Prerequisites:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700501
502 1. Ethtool support in the base drivers for retrieving
503 the speed and duplex of each slave.
504
505 2. A switch that supports IEEE 802.3ad Dynamic link
506 aggregation.
507
508 Most switches will require some type of configuration
509 to enable 802.3ad mode.
510
511 balance-tlb or 5
512
513 Adaptive transmit load balancing: channel bonding that
514 does not require any special switch support. The
515 outgoing traffic is distributed according to the
516 current load (computed relative to the speed) on each
517 slave. Incoming traffic is received by the current
518 slave. If the receiving slave fails, another slave
519 takes over the MAC address of the failed receiving
520 slave.
521
522 Prerequisite:
523
524 Ethtool support in the base drivers for retrieving the
525 speed of each slave.
526
527 balance-alb or 6
528
529 Adaptive load balancing: includes balance-tlb plus
530 receive load balancing (rlb) for IPV4 traffic, and
531 does not require any special switch support. The
532 receive load balancing is achieved by ARP negotiation.
533 The bonding driver intercepts the ARP Replies sent by
534 the local system on their way out and overwrites the
535 source hardware address with the unique hardware
536 address of one of the slaves in the bond such that
537 different peers use different hardware addresses for
538 the server.
539
540 Receive traffic from connections created by the server
541 is also balanced. When the local system sends an ARP
542 Request the bonding driver copies and saves the peer's
543 IP information from the ARP packet. When the ARP
544 Reply arrives from the peer, its hardware address is
545 retrieved and the bonding driver initiates an ARP
546 reply to this peer assigning it to one of the slaves
547 in the bond. A problematic outcome of using ARP
548 negotiation for balancing is that each time that an
549 ARP request is broadcast it uses the hardware address
550 of the bond. Hence, peers learn the hardware address
551 of the bond and the balancing of receive traffic
552 collapses to the current slave. This is handled by
553 sending updates (ARP Replies) to all the peers with
554 their individually assigned hardware address such that
555 the traffic is redistributed. Receive traffic is also
556 redistributed when a new slave is added to the bond
557 and when an inactive slave is re-activated. The
558 receive load is distributed sequentially (round robin)
559 among the group of highest speed slaves in the bond.
560
561 When a link is reconnected or a new slave joins the
562 bond the receive traffic is redistributed among all
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700563 active slaves in the bond by initiating ARP Replies
Auke Kok6224e012006-06-08 11:15:35 -0700564 with the selected MAC address to each of the
Linus Torvalds1da177e2005-04-16 15:20:36 -0700565 clients. The updelay parameter (detailed below) must
566 be set to a value equal or greater than the switch's
567 forwarding delay so that the ARP Replies sent to the
568 peers will not be blocked by the switch.
569
570 Prerequisites:
571
572 1. Ethtool support in the base drivers for retrieving
573 the speed of each slave.
574
575 2. Base driver support for setting the hardware
576 address of a device while it is open. This is
577 required so that there will always be one slave in the
578 team using the bond hardware address (the
579 curr_active_slave) while having a unique hardware
580 address for each slave in the bond. If the
581 curr_active_slave fails its hardware address is
582 swapped with the new curr_active_slave that was
583 chosen.
584
Jay Vosburghb59f9f72008-06-13 18:12:03 -0700585num_grat_arp
586
587 Specifies the number of gratuitous ARPs to be issued after a
588 failover event. One gratuitous ARP is issued immediately after
589 the failover, subsequent ARPs are sent at a rate of one per link
590 monitor interval (arp_interval or miimon, whichever is active).
591
592 The valid range is 0 - 255; the default value is 1. This option
593 affects only the active-backup mode. This option was added for
594 bonding version 3.3.0.
595
Brian Haley305d5522008-11-04 17:51:14 -0800596num_unsol_na
597
598 Specifies the number of unsolicited IPv6 Neighbor Advertisements
599 to be issued after a failover event. One unsolicited NA is issued
600 immediately after the failover.
601
602 The valid range is 0 - 255; the default value is 1. This option
603 affects only the active-backup mode. This option was added for
604 bonding version 3.4.0.
605
Linus Torvalds1da177e2005-04-16 15:20:36 -0700606primary
607
608 A string (eth0, eth2, etc) specifying which slave is the
609 primary device. The specified device will always be the
610 active slave while it is available. Only when the primary is
611 off-line will alternate devices be used. This is useful when
612 one slave is preferred over another, e.g., when one slave has
613 higher throughput than another.
614
615 The primary option is only valid for active-backup mode.
616
617updelay
618
619 Specifies the time, in milliseconds, to wait before enabling a
620 slave after a link recovery has been detected. This option is
621 only valid for the miimon link monitor. The updelay value
622 should be a multiple of the miimon value; if not, it will be
623 rounded down to the nearest multiple. The default value is 0.
624
625use_carrier
626
627 Specifies whether or not miimon should use MII or ETHTOOL
628 ioctls vs. netif_carrier_ok() to determine the link
629 status. The MII or ETHTOOL ioctls are less efficient and
630 utilize a deprecated calling sequence within the kernel. The
631 netif_carrier_ok() relies on the device driver to maintain its
632 state with netif_carrier_on/off; at this writing, most, but
633 not all, device drivers support this facility.
634
635 If bonding insists that the link is up when it should not be,
636 it may be that your network device driver does not support
637 netif_carrier_on/off. The default state for netif_carrier is
638 "carrier on," so if a driver does not support netif_carrier,
639 it will appear as if the link is always up. In this case,
640 setting use_carrier to 0 will cause bonding to revert to the
641 MII / ETHTOOL ioctl method to determine the link state.
642
643 A value of 1 enables the use of netif_carrier_ok(), a value of
644 0 will use the deprecated MII / ETHTOOL ioctls. The default
645 value is 1.
646
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700647xmit_hash_policy
648
649 Selects the transmit hash policy to use for slave selection in
650 balance-xor and 802.3ad modes. Possible values are:
651
652 layer2
653
654 Uses XOR of hardware MAC addresses to generate the
655 hash. The formula is
656
657 (source MAC XOR destination MAC) modulo slave count
658
659 This algorithm will place all traffic to a particular
660 network peer on the same slave.
661
662 This algorithm is 802.3ad compliant.
663
Jay Vosburgh6f6652b2007-12-06 23:40:34 -0800664 layer2+3
665
666 This policy uses a combination of layer2 and layer3
667 protocol information to generate the hash.
668
669 Uses XOR of hardware MAC addresses and IP addresses to
670 generate the hash. The formula is
671
672 (((source IP XOR dest IP) AND 0xffff) XOR
673 ( source MAC XOR destination MAC ))
674 modulo slave count
675
676 This algorithm will place all traffic to a particular
677 network peer on the same slave. For non-IP traffic,
678 the formula is the same as for the layer2 transmit
679 hash policy.
680
681 This policy is intended to provide a more balanced
682 distribution of traffic than layer2 alone, especially
683 in environments where a layer3 gateway device is
684 required to reach most destinations.
685
Matt LaPlanted9195882008-07-25 19:45:33 -0700686 This algorithm is 802.3ad compliant.
Jay Vosburgh6f6652b2007-12-06 23:40:34 -0800687
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700688 layer3+4
689
690 This policy uses upper layer protocol information,
691 when available, to generate the hash. This allows for
692 traffic to a particular network peer to span multiple
693 slaves, although a single connection will not span
694 multiple slaves.
695
696 The formula for unfragmented TCP and UDP packets is
697
698 ((source port XOR dest port) XOR
699 ((source IP XOR dest IP) AND 0xffff)
700 modulo slave count
701
702 For fragmented TCP or UDP packets and all other IP
703 protocol traffic, the source and destination port
704 information is omitted. For non-IP traffic, the
705 formula is the same as for the layer2 transmit hash
706 policy.
707
708 This policy is intended to mimic the behavior of
709 certain switches, notably Cisco switches with PFC2 as
710 well as some Foundry and IBM products.
711
712 This algorithm is not fully 802.3ad compliant. A
713 single TCP or UDP conversation containing both
714 fragmented and unfragmented packets will see packets
715 striped across two interfaces. This may result in out
716 of order delivery. Most traffic types will not meet
717 this criteria, as TCP rarely fragments traffic, and
718 most UDP traffic is not involved in extended
719 conversations. Other implementations of 802.3ad may
720 or may not tolerate this noncompliance.
721
722 The default value is layer2. This option was added in bonding
Jay Vosburgh6f6652b2007-12-06 23:40:34 -0800723 version 2.6.3. In earlier versions of bonding, this parameter
724 does not exist, and the layer2 policy is the only policy. The
725 layer2+3 value was added for bonding version 3.2.2.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700726
727
7283. Configuring Bonding Devices
729==============================
730
Auke Kok6224e012006-06-08 11:15:35 -0700731 You can configure bonding using either your distro's network
732initialization scripts, or manually using either ifenslave or the
733sysfs interface. Distros generally use one of two packages for the
734network initialization scripts: initscripts or sysconfig. Recent
735versions of these packages have support for bonding, while older
736versions do not.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700737
738 We will first describe the options for configuring bonding for
739distros using versions of initscripts and sysconfig with full or
740partial support for bonding, then provide information on enabling
741bonding without support from the network initialization scripts (i.e.,
742older versions of initscripts or sysconfig).
743
744 If you're unsure whether your distro uses sysconfig or
745initscripts, or don't know if it's new enough, have no fear.
746Determining this is fairly straightforward.
747
748 First, issue the command:
749
750$ rpm -qf /sbin/ifup
751
752 It will respond with a line of text starting with either
753"initscripts" or "sysconfig," followed by some numbers. This is the
754package that provides your network initialization scripts.
755
756 Next, to determine if your installation supports bonding,
757issue the command:
758
759$ grep ifenslave /sbin/ifup
760
761 If this returns any matches, then your initscripts or
762sysconfig has support for bonding.
763
Auke Kok6224e012006-06-08 11:15:35 -07007643.1 Configuration with Sysconfig Support
Linus Torvalds1da177e2005-04-16 15:20:36 -0700765----------------------------------------
766
767 This section applies to distros using a version of sysconfig
768with bonding support, for example, SuSE Linux Enterprise Server 9.
769
770 SuSE SLES 9's networking configuration system does support
771bonding, however, at this writing, the YaST system configuration
Auke Kok6224e012006-06-08 11:15:35 -0700772front end does not provide any means to work with bonding devices.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700773Bonding devices can be managed by hand, however, as follows.
774
775 First, if they have not already been configured, configure the
776slave devices. On SLES 9, this is most easily done by running the
777yast2 sysconfig configuration utility. The goal is for to create an
778ifcfg-id file for each slave device. The simplest way to accomplish
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700779this is to configure the devices for DHCP (this is only to get the
780file ifcfg-id file created; see below for some issues with DHCP). The
781name of the configuration file for each device will be of the form:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700782
783ifcfg-id-xx:xx:xx:xx:xx:xx
784
785 Where the "xx" portion will be replaced with the digits from
786the device's permanent MAC address.
787
788 Once the set of ifcfg-id-xx:xx:xx:xx:xx:xx files has been
789created, it is necessary to edit the configuration files for the slave
790devices (the MAC addresses correspond to those of the slave devices).
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700791Before editing, the file will contain multiple lines, and will look
Linus Torvalds1da177e2005-04-16 15:20:36 -0700792something like this:
793
794BOOTPROTO='dhcp'
795STARTMODE='on'
796USERCTL='no'
797UNIQUE='XNzu.WeZGOGF+4wE'
798_nm_name='bus-pci-0001:61:01.0'
799
800 Change the BOOTPROTO and STARTMODE lines to the following:
801
802BOOTPROTO='none'
803STARTMODE='off'
804
805 Do not alter the UNIQUE or _nm_name lines. Remove any other
806lines (USERCTL, etc).
807
808 Once the ifcfg-id-xx:xx:xx:xx:xx:xx files have been modified,
809it's time to create the configuration file for the bonding device
810itself. This file is named ifcfg-bondX, where X is the number of the
811bonding device to create, starting at 0. The first such file is
812ifcfg-bond0, the second is ifcfg-bond1, and so on. The sysconfig
813network configuration system will correctly start multiple instances
814of bonding.
815
816 The contents of the ifcfg-bondX file is as follows:
817
818BOOTPROTO="static"
819BROADCAST="10.0.2.255"
820IPADDR="10.0.2.10"
821NETMASK="255.255.0.0"
822NETWORK="10.0.2.0"
823REMOTE_IPADDR=""
824STARTMODE="onboot"
825BONDING_MASTER="yes"
826BONDING_MODULE_OPTS="mode=active-backup miimon=100"
827BONDING_SLAVE0="eth0"
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700828BONDING_SLAVE1="bus-pci-0000:06:08.1"
Linus Torvalds1da177e2005-04-16 15:20:36 -0700829
830 Replace the sample BROADCAST, IPADDR, NETMASK and NETWORK
831values with the appropriate values for your network.
832
Linus Torvalds1da177e2005-04-16 15:20:36 -0700833 The STARTMODE specifies when the device is brought online.
834The possible values are:
835
836 onboot: The device is started at boot time. If you're not
837 sure, this is probably what you want.
838
839 manual: The device is started only when ifup is called
840 manually. Bonding devices may be configured this
841 way if you do not wish them to start automatically
842 at boot for some reason.
843
844 hotplug: The device is started by a hotplug event. This is not
845 a valid choice for a bonding device.
846
847 off or ignore: The device configuration is ignored.
848
849 The line BONDING_MASTER='yes' indicates that the device is a
850bonding master device. The only useful value is "yes."
851
852 The contents of BONDING_MODULE_OPTS are supplied to the
853instance of the bonding module for this device. Specify the options
854for the bonding mode, link monitoring, and so on here. Do not include
855the max_bonds bonding parameter; this will confuse the configuration
856system if you have multiple bonding devices.
857
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700858 Finally, supply one BONDING_SLAVEn="slave device" for each
859slave. where "n" is an increasing value, one for each slave. The
860"slave device" is either an interface name, e.g., "eth0", or a device
861specifier for the network device. The interface name is easier to
862find, but the ethN names are subject to change at boot time if, e.g.,
863a device early in the sequence has failed. The device specifiers
864(bus-pci-0000:06:08.1 in the example above) specify the physical
865network device, and will not change unless the device's bus location
866changes (for example, it is moved from one PCI slot to another). The
867example above uses one of each type for demonstration purposes; most
868configurations will choose one or the other for all slave devices.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700869
870 When all configuration files have been modified or created,
871networking must be restarted for the configuration changes to take
872effect. This can be accomplished via the following:
873
874# /etc/init.d/network restart
875
876 Note that the network control script (/sbin/ifdown) will
877remove the bonding module as part of the network shutdown processing,
878so it is not necessary to remove the module by hand if, e.g., the
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700879module parameters have changed.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700880
881 Also, at this writing, YaST/YaST2 will not manage bonding
882devices (they do not show bonding interfaces on its list of network
883devices). It is necessary to edit the configuration file by hand to
884change the bonding configuration.
885
886 Additional general options and details of the ifcfg file
887format can be found in an example ifcfg template file:
888
889/etc/sysconfig/network/ifcfg.template
890
891 Note that the template does not document the various BONDING_
892settings described above, but does describe many of the other options.
893
Auke Kok6224e012006-06-08 11:15:35 -07008943.1.1 Using DHCP with Sysconfig
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700895-------------------------------
896
897 Under sysconfig, configuring a device with BOOTPROTO='dhcp'
898will cause it to query DHCP for its IP address information. At this
899writing, this does not function for bonding devices; the scripts
900attempt to obtain the device address from DHCP prior to adding any of
901the slave devices. Without active slaves, the DHCP requests are not
902sent to the network.
903
Auke Kok6224e012006-06-08 11:15:35 -07009043.1.2 Configuring Multiple Bonds with Sysconfig
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700905-----------------------------------------------
906
907 The sysconfig network initialization system is capable of
908handling multiple bonding devices. All that is necessary is for each
909bonding instance to have an appropriately configured ifcfg-bondX file
910(as described above). Do not specify the "max_bonds" parameter to any
911instance of bonding, as this will confuse sysconfig. If you require
912multiple bonding devices with identical parameters, create multiple
913ifcfg-bondX files.
914
915 Because the sysconfig scripts supply the bonding module
916options in the ifcfg-bondX file, it is not necessary to add them to
917the system /etc/modules.conf or /etc/modprobe.conf configuration file.
918
Auke Kok6224e012006-06-08 11:15:35 -07009193.2 Configuration with Initscripts Support
Linus Torvalds1da177e2005-04-16 15:20:36 -0700920------------------------------------------
921
Jay Vosburgh9a6c6862007-11-13 20:25:48 -0800922 This section applies to distros using a recent version of
923initscripts with bonding support, for example, Red Hat Enterprise Linux
924version 3 or later, Fedora, etc. On these systems, the network
925initialization scripts have knowledge of bonding, and can be configured to
926control bonding devices. Note that older versions of the initscripts
927package have lower levels of support for bonding; this will be noted where
928applicable.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700929
930 These distros will not automatically load the network adapter
931driver unless the ethX device is configured with an IP address.
932Because of this constraint, users must manually configure a
933network-script file for all physical adapters that will be members of
934a bondX link. Network script files are located in the directory:
935
936/etc/sysconfig/network-scripts
937
938 The file name must be prefixed with "ifcfg-eth" and suffixed
939with the adapter's physical adapter number. For example, the script
940for eth0 would be named /etc/sysconfig/network-scripts/ifcfg-eth0.
941Place the following text in the file:
942
943DEVICE=eth0
944USERCTL=no
945ONBOOT=yes
946MASTER=bond0
947SLAVE=yes
948BOOTPROTO=none
949
950 The DEVICE= line will be different for every ethX device and
951must correspond with the name of the file, i.e., ifcfg-eth1 must have
952a device line of DEVICE=eth1. The setting of the MASTER= line will
953also depend on the final bonding interface name chosen for your bond.
954As with other network devices, these typically start at 0, and go up
955one for each device, i.e., the first bonding instance is bond0, the
956second is bond1, and so on.
957
958 Next, create a bond network script. The file name for this
959script will be /etc/sysconfig/network-scripts/ifcfg-bondX where X is
960the number of the bond. For bond0 the file is named "ifcfg-bond0",
961for bond1 it is named "ifcfg-bond1", and so on. Within that file,
962place the following text:
963
964DEVICE=bond0
965IPADDR=192.168.1.1
966NETMASK=255.255.255.0
967NETWORK=192.168.1.0
968BROADCAST=192.168.1.255
969ONBOOT=yes
970BOOTPROTO=none
971USERCTL=no
972
973 Be sure to change the networking specific lines (IPADDR,
974NETMASK, NETWORK and BROADCAST) to match your network configuration.
975
Jay Vosburgh9a6c6862007-11-13 20:25:48 -0800976 For later versions of initscripts, such as that found with Fedora
Andy Gospodarek3f8b4b12008-10-22 11:19:48 +00009777 (or later) and Red Hat Enterprise Linux version 5 (or later), it is possible,
978and, indeed, preferable, to specify the bonding options in the ifcfg-bond0
Jay Vosburgh9a6c6862007-11-13 20:25:48 -0800979file, e.g. a line of the format:
980
Andy Gospodarek3f8b4b12008-10-22 11:19:48 +0000981BONDING_OPTS="mode=active-backup arp_interval=60 arp_ip_target=192.168.1.254"
Jay Vosburgh9a6c6862007-11-13 20:25:48 -0800982
983 will configure the bond with the specified options. The options
984specified in BONDING_OPTS are identical to the bonding module parameters
Andy Gospodarek3f8b4b12008-10-22 11:19:48 +0000985except for the arp_ip_target field when using versions of initscripts older
986than and 8.57 (Fedora 8) and 8.45.19 (Red Hat Enterprise Linux 5.2). When
987using older versions each target should be included as a separate option and
988should be preceded by a '+' to indicate it should be added to the list of
989queried targets, e.g.,
Jay Vosburgh9a6c6862007-11-13 20:25:48 -0800990
991 arp_ip_target=+192.168.1.1 arp_ip_target=+192.168.1.2
992
993 is the proper syntax to specify multiple targets. When specifying
994options via BONDING_OPTS, it is not necessary to edit /etc/modules.conf or
995/etc/modprobe.conf.
996
Andy Gospodarek3f8b4b12008-10-22 11:19:48 +0000997 For even older versions of initscripts that do not support
Jay Vosburgh9a6c6862007-11-13 20:25:48 -0800998BONDING_OPTS, it is necessary to edit /etc/modules.conf (or
999/etc/modprobe.conf, depending upon your distro) to load the bonding module
1000with your desired options when the bond0 interface is brought up. The
1001following lines in /etc/modules.conf (or modprobe.conf) will load the
1002bonding module, and select its options:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001003
1004alias bond0 bonding
1005options bond0 mode=balance-alb miimon=100
1006
1007 Replace the sample parameters with the appropriate set of
1008options for your configuration.
1009
1010 Finally run "/etc/rc.d/init.d/network restart" as root. This
1011will restart the networking subsystem and your bond link should be now
1012up and running.
1013
Auke Kok6224e012006-06-08 11:15:35 -070010143.2.1 Using DHCP with Initscripts
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001015---------------------------------
1016
Jay Vosburgh9a6c6862007-11-13 20:25:48 -08001017 Recent versions of initscripts (the versions supplied with Fedora
1018Core 3 and Red Hat Enterprise Linux 4, or later versions, are reported to
1019work) have support for assigning IP information to bonding devices via
1020DHCP.
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001021
1022 To configure bonding for DHCP, configure it as described
1023above, except replace the line "BOOTPROTO=none" with "BOOTPROTO=dhcp"
1024and add a line consisting of "TYPE=Bonding". Note that the TYPE value
1025is case sensitive.
1026
Auke Kok6224e012006-06-08 11:15:35 -070010273.2.2 Configuring Multiple Bonds with Initscripts
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001028-------------------------------------------------
1029
Jay Vosburgh9a6c6862007-11-13 20:25:48 -08001030 Initscripts packages that are included with Fedora 7 and Red Hat
1031Enterprise Linux 5 support multiple bonding interfaces by simply
1032specifying the appropriate BONDING_OPTS= in ifcfg-bondX where X is the
1033number of the bond. This support requires sysfs support in the kernel,
1034and a bonding driver of version 3.0.0 or later. Other configurations may
1035not support this method for specifying multiple bonding interfaces; for
1036those instances, see the "Configuring Multiple Bonds Manually" section,
1037below.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001038
Auke Kok6224e012006-06-08 11:15:35 -070010393.3 Configuring Bonding Manually with Ifenslave
1040-----------------------------------------------
Linus Torvalds1da177e2005-04-16 15:20:36 -07001041
1042 This section applies to distros whose network initialization
1043scripts (the sysconfig or initscripts package) do not have specific
1044knowledge of bonding. One such distro is SuSE Linux Enterprise Server
1045version 8.
1046
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001047 The general method for these systems is to place the bonding
1048module parameters into /etc/modules.conf or /etc/modprobe.conf (as
1049appropriate for the installed distro), then add modprobe and/or
1050ifenslave commands to the system's global init script. The name of
1051the global init script differs; for sysconfig, it is
Linus Torvalds1da177e2005-04-16 15:20:36 -07001052/etc/init.d/boot.local and for initscripts it is /etc/rc.d/rc.local.
1053
1054 For example, if you wanted to make a simple bond of two e100
1055devices (presumed to be eth0 and eth1), and have it persist across
1056reboots, edit the appropriate file (/etc/init.d/boot.local or
1057/etc/rc.d/rc.local), and add the following:
1058
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001059modprobe bonding mode=balance-alb miimon=100
Linus Torvalds1da177e2005-04-16 15:20:36 -07001060modprobe e100
1061ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up
1062ifenslave bond0 eth0
1063ifenslave bond0 eth1
1064
1065 Replace the example bonding module parameters and bond0
1066network configuration (IP address, netmask, etc) with the appropriate
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001067values for your configuration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001068
1069 Unfortunately, this method will not provide support for the
1070ifup and ifdown scripts on the bond devices. To reload the bonding
1071configuration, it is necessary to run the initialization script, e.g.,
1072
1073# /etc/init.d/boot.local
1074
1075 or
1076
1077# /etc/rc.d/rc.local
1078
1079 It may be desirable in such a case to create a separate script
1080which only initializes the bonding configuration, then call that
1081separate script from within boot.local. This allows for bonding to be
1082enabled without re-running the entire global init script.
1083
1084 To shut down the bonding devices, it is necessary to first
1085mark the bonding device itself as being down, then remove the
1086appropriate device driver modules. For our example above, you can do
1087the following:
1088
1089# ifconfig bond0 down
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001090# rmmod bonding
Linus Torvalds1da177e2005-04-16 15:20:36 -07001091# rmmod e100
1092
1093 Again, for convenience, it may be desirable to create a script
1094with these commands.
1095
1096
Jay Vosburgh00354cf2005-07-21 12:18:02 -070010973.3.1 Configuring Multiple Bonds Manually
1098-----------------------------------------
Linus Torvalds1da177e2005-04-16 15:20:36 -07001099
1100 This section contains information on configuring multiple
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001101bonding devices with differing options for those systems whose network
1102initialization scripts lack support for configuring multiple bonds.
1103
1104 If you require multiple bonding devices, but all with the same
1105options, you may wish to use the "max_bonds" module parameter,
1106documented above.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001107
Jay Vosburgh9a6c6862007-11-13 20:25:48 -08001108 To create multiple bonding devices with differing options, it is
1109preferrable to use bonding parameters exported by sysfs, documented in the
1110section below.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001111
Jay Vosburgh9a6c6862007-11-13 20:25:48 -08001112 For versions of bonding without sysfs support, the only means to
1113provide multiple instances of bonding with differing options is to load
1114the bonding driver multiple times. Note that current versions of the
1115sysconfig network initialization scripts handle this automatically; if
1116your distro uses these scripts, no special action is needed. See the
1117section Configuring Bonding Devices, above, if you're not sure about your
1118network initialization scripts.
1119
1120 To load multiple instances of the module, it is necessary to
1121specify a different name for each instance (the module loading system
1122requires that every loaded module, even multiple instances of the same
1123module, have a unique name). This is accomplished by supplying multiple
1124sets of bonding options in /etc/modprobe.conf, for example:
1125
1126alias bond0 bonding
1127options bond0 -o bond0 mode=balance-rr miimon=100
1128
1129alias bond1 bonding
1130options bond1 -o bond1 mode=balance-alb miimon=50
1131
1132 will load the bonding module two times. The first instance is
1133named "bond0" and creates the bond0 device in balance-rr mode with an
1134miimon of 100. The second instance is named "bond1" and creates the
1135bond1 device in balance-alb mode with an miimon of 50.
1136
1137 In some circumstances (typically with older distributions),
1138the above does not work, and the second bonding instance never sees
1139its options. In that case, the second options line can be substituted
1140as follows:
1141
1142install bond1 /sbin/modprobe --ignore-install bonding -o bond1 \
1143 mode=balance-alb miimon=50
1144
1145 This may be repeated any number of times, specifying a new and
1146unique name in place of bond1 for each subsequent instance.
1147
1148 It has been observed that some Red Hat supplied kernels are unable
1149to rename modules at load time (the "-o bond1" part). Attempts to pass
1150that option to modprobe will produce an "Operation not permitted" error.
1151This has been reported on some Fedora Core kernels, and has been seen on
1152RHEL 4 as well. On kernels exhibiting this problem, it will be impossible
1153to configure multiple bonds with differing parameters (as they are older
1154kernels, and also lack sysfs support).
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001155
Auke Kok6224e012006-06-08 11:15:35 -070011563.4 Configuring Bonding Manually via Sysfs
1157------------------------------------------
Linus Torvalds1da177e2005-04-16 15:20:36 -07001158
Jay Vosburgh9a6c6862007-11-13 20:25:48 -08001159 Starting with version 3.0.0, Channel Bonding may be configured
Auke Kok6224e012006-06-08 11:15:35 -07001160via the sysfs interface. This interface allows dynamic configuration
1161of all bonds in the system without unloading the module. It also
1162allows for adding and removing bonds at runtime. Ifenslave is no
1163longer required, though it is still supported.
1164
1165 Use of the sysfs interface allows you to use multiple bonds
1166with different configurations without having to reload the module.
1167It also allows you to use multiple, differently configured bonds when
1168bonding is compiled into the kernel.
1169
1170 You must have the sysfs filesystem mounted to configure
1171bonding this way. The examples in this document assume that you
1172are using the standard mount point for sysfs, e.g. /sys. If your
1173sysfs filesystem is mounted elsewhere, you will need to adjust the
1174example paths accordingly.
1175
1176Creating and Destroying Bonds
1177-----------------------------
1178To add a new bond foo:
1179# echo +foo > /sys/class/net/bonding_masters
1180
1181To remove an existing bond bar:
1182# echo -bar > /sys/class/net/bonding_masters
1183
1184To show all existing bonds:
1185# cat /sys/class/net/bonding_masters
1186
1187NOTE: due to 4K size limitation of sysfs files, this list may be
1188truncated if you have more than a few hundred bonds. This is unlikely
1189to occur under normal operating conditions.
1190
1191Adding and Removing Slaves
1192--------------------------
1193 Interfaces may be enslaved to a bond using the file
1194/sys/class/net/<bond>/bonding/slaves. The semantics for this file
1195are the same as for the bonding_masters file.
1196
1197To enslave interface eth0 to bond bond0:
1198# ifconfig bond0 up
1199# echo +eth0 > /sys/class/net/bond0/bonding/slaves
1200
1201To free slave eth0 from bond bond0:
1202# echo -eth0 > /sys/class/net/bond0/bonding/slaves
1203
Auke Kok6224e012006-06-08 11:15:35 -07001204 When an interface is enslaved to a bond, symlinks between the
1205two are created in the sysfs filesystem. In this case, you would get
1206/sys/class/net/bond0/slave_eth0 pointing to /sys/class/net/eth0, and
1207/sys/class/net/eth0/master pointing to /sys/class/net/bond0.
1208
1209 This means that you can tell quickly whether or not an
1210interface is enslaved by looking for the master symlink. Thus:
1211# echo -eth0 > /sys/class/net/eth0/master/bonding/slaves
1212will free eth0 from whatever bond it is enslaved to, regardless of
1213the name of the bond interface.
1214
1215Changing a Bond's Configuration
1216-------------------------------
1217 Each bond may be configured individually by manipulating the
1218files located in /sys/class/net/<bond name>/bonding
1219
1220 The names of these files correspond directly with the command-
Paolo Ornati670e9f32006-10-03 22:57:56 +02001221line parameters described elsewhere in this file, and, with the
Auke Kok6224e012006-06-08 11:15:35 -07001222exception of arp_ip_target, they accept the same values. To see the
1223current setting, simply cat the appropriate file.
1224
1225 A few examples will be given here; for specific usage
1226guidelines for each parameter, see the appropriate section in this
1227document.
1228
1229To configure bond0 for balance-alb mode:
1230# ifconfig bond0 down
1231# echo 6 > /sys/class/net/bond0/bonding/mode
1232 - or -
1233# echo balance-alb > /sys/class/net/bond0/bonding/mode
1234 NOTE: The bond interface must be down before the mode can be
1235changed.
1236
1237To enable MII monitoring on bond0 with a 1 second interval:
1238# echo 1000 > /sys/class/net/bond0/bonding/miimon
1239 NOTE: If ARP monitoring is enabled, it will disabled when MII
1240monitoring is enabled, and vice-versa.
1241
1242To add ARP targets:
1243# echo +192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target
1244# echo +192.168.0.101 > /sys/class/net/bond0/bonding/arp_ip_target
1245 NOTE: up to 10 target addresses may be specified.
1246
1247To remove an ARP target:
1248# echo -192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target
1249
1250Example Configuration
1251---------------------
1252 We begin with the same example that is shown in section 3.3,
1253executed with sysfs, and without using ifenslave.
1254
1255 To make a simple bond of two e100 devices (presumed to be eth0
1256and eth1), and have it persist across reboots, edit the appropriate
1257file (/etc/init.d/boot.local or /etc/rc.d/rc.local), and add the
1258following:
1259
1260modprobe bonding
1261modprobe e100
1262echo balance-alb > /sys/class/net/bond0/bonding/mode
1263ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up
1264echo 100 > /sys/class/net/bond0/bonding/miimon
1265echo +eth0 > /sys/class/net/bond0/bonding/slaves
1266echo +eth1 > /sys/class/net/bond0/bonding/slaves
1267
1268 To add a second bond, with two e1000 interfaces in
1269active-backup mode, using ARP monitoring, add the following lines to
1270your init script:
1271
1272modprobe e1000
1273echo +bond1 > /sys/class/net/bonding_masters
1274echo active-backup > /sys/class/net/bond1/bonding/mode
1275ifconfig bond1 192.168.2.1 netmask 255.255.255.0 up
1276echo +192.168.2.100 /sys/class/net/bond1/bonding/arp_ip_target
1277echo 2000 > /sys/class/net/bond1/bonding/arp_interval
1278echo +eth2 > /sys/class/net/bond1/bonding/slaves
1279echo +eth3 > /sys/class/net/bond1/bonding/slaves
1280
1281
12824. Querying Bonding Configuration
Linus Torvalds1da177e2005-04-16 15:20:36 -07001283=================================
1284
Auke Kok6224e012006-06-08 11:15:35 -070012854.1 Bonding Configuration
Linus Torvalds1da177e2005-04-16 15:20:36 -07001286-------------------------
1287
1288 Each bonding device has a read-only file residing in the
1289/proc/net/bonding directory. The file contents include information
1290about the bonding configuration, options and state of each slave.
1291
1292 For example, the contents of /proc/net/bonding/bond0 after the
1293driver is loaded with parameters of mode=0 and miimon=1000 is
1294generally as follows:
1295
1296 Ethernet Channel Bonding Driver: 2.6.1 (October 29, 2004)
1297 Bonding Mode: load balancing (round-robin)
1298 Currently Active Slave: eth0
1299 MII Status: up
1300 MII Polling Interval (ms): 1000
1301 Up Delay (ms): 0
1302 Down Delay (ms): 0
1303
1304 Slave Interface: eth1
1305 MII Status: up
1306 Link Failure Count: 1
1307
1308 Slave Interface: eth0
1309 MII Status: up
1310 Link Failure Count: 1
1311
1312 The precise format and contents will change depending upon the
1313bonding configuration, state, and version of the bonding driver.
1314
Auke Kok6224e012006-06-08 11:15:35 -070013154.2 Network configuration
Linus Torvalds1da177e2005-04-16 15:20:36 -07001316-------------------------
1317
1318 The network configuration can be inspected using the ifconfig
1319command. Bonding devices will have the MASTER flag set; Bonding slave
1320devices will have the SLAVE flag set. The ifconfig output does not
1321contain information on which slaves are associated with which masters.
1322
1323 In the example below, the bond0 interface is the master
1324(MASTER) while eth0 and eth1 are slaves (SLAVE). Notice all slaves of
1325bond0 have the same MAC address (HWaddr) as bond0 for all modes except
1326TLB and ALB that require a unique MAC address for each slave.
1327
1328# /sbin/ifconfig
1329bond0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
1330 inet addr:XXX.XXX.XXX.YYY Bcast:XXX.XXX.XXX.255 Mask:255.255.252.0
1331 UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1
1332 RX packets:7224794 errors:0 dropped:0 overruns:0 frame:0
1333 TX packets:3286647 errors:1 dropped:0 overruns:1 carrier:0
1334 collisions:0 txqueuelen:0
1335
1336eth0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
Linus Torvalds1da177e2005-04-16 15:20:36 -07001337 UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
1338 RX packets:3573025 errors:0 dropped:0 overruns:0 frame:0
1339 TX packets:1643167 errors:1 dropped:0 overruns:1 carrier:0
1340 collisions:0 txqueuelen:100
1341 Interrupt:10 Base address:0x1080
1342
1343eth1 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
Linus Torvalds1da177e2005-04-16 15:20:36 -07001344 UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
1345 RX packets:3651769 errors:0 dropped:0 overruns:0 frame:0
1346 TX packets:1643480 errors:0 dropped:0 overruns:0 carrier:0
1347 collisions:0 txqueuelen:100
1348 Interrupt:9 Base address:0x1400
1349
Auke Kok6224e012006-06-08 11:15:35 -070013505. Switch Configuration
Linus Torvalds1da177e2005-04-16 15:20:36 -07001351=======================
1352
1353 For this section, "switch" refers to whatever system the
1354bonded devices are directly connected to (i.e., where the other end of
1355the cable plugs into). This may be an actual dedicated switch device,
1356or it may be another regular system (e.g., another computer running
1357Linux),
1358
1359 The active-backup, balance-tlb and balance-alb modes do not
1360require any specific configuration of the switch.
1361
1362 The 802.3ad mode requires that the switch have the appropriate
1363ports configured as an 802.3ad aggregation. The precise method used
1364to configure this varies from switch to switch, but, for example, a
1365Cisco 3550 series switch requires that the appropriate ports first be
1366grouped together in a single etherchannel instance, then that
1367etherchannel is set to mode "lacp" to enable 802.3ad (instead of
1368standard EtherChannel).
1369
1370 The balance-rr, balance-xor and broadcast modes generally
1371require that the switch have the appropriate ports grouped together.
1372The nomenclature for such a group differs between switches, it may be
1373called an "etherchannel" (as in the Cisco example, above), a "trunk
1374group" or some other similar variation. For these modes, each switch
1375will also have its own configuration options for the switch's transmit
1376policy to the bond. Typical choices include XOR of either the MAC or
1377IP addresses. The transmit policy of the two peers does not need to
1378match. For these three modes, the bonding mode really selects a
1379transmit policy for an EtherChannel group; all three will interoperate
1380with another EtherChannel group.
1381
1382
Auke Kok6224e012006-06-08 11:15:35 -070013836. 802.1q VLAN Support
Linus Torvalds1da177e2005-04-16 15:20:36 -07001384======================
1385
1386 It is possible to configure VLAN devices over a bond interface
1387using the 8021q driver. However, only packets coming from the 8021q
1388driver and passing through bonding will be tagged by default. Self
1389generated packets, for example, bonding's learning packets or ARP
1390packets generated by either ALB mode or the ARP monitor mechanism, are
1391tagged internally by bonding itself. As a result, bonding must
1392"learn" the VLAN IDs configured above it, and use those IDs to tag
1393self generated packets.
1394
1395 For reasons of simplicity, and to support the use of adapters
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001396that can do VLAN hardware acceleration offloading, the bonding
1397interface declares itself as fully hardware offloading capable, it gets
Linus Torvalds1da177e2005-04-16 15:20:36 -07001398the add_vid/kill_vid notifications to gather the necessary
1399information, and it propagates those actions to the slaves. In case
1400of mixed adapter types, hardware accelerated tagged packets that
1401should go through an adapter that is not offloading capable are
1402"un-accelerated" by the bonding driver so the VLAN tag sits in the
1403regular location.
1404
1405 VLAN interfaces *must* be added on top of a bonding interface
1406only after enslaving at least one slave. The bonding interface has a
1407hardware address of 00:00:00:00:00:00 until the first slave is added.
1408If the VLAN interface is created prior to the first enslavement, it
1409would pick up the all-zeroes hardware address. Once the first slave
1410is attached to the bond, the bond device itself will pick up the
1411slave's hardware address, which is then available for the VLAN device.
1412
1413 Also, be aware that a similar problem can occur if all slaves
1414are released from a bond that still has one or more VLAN interfaces on
1415top of it. When a new slave is added, the bonding interface will
1416obtain its hardware address from the first slave, which might not
1417match the hardware address of the VLAN interfaces (which was
1418ultimately copied from an earlier slave).
1419
1420 There are two methods to insure that the VLAN device operates
1421with the correct hardware address if all slaves are removed from a
1422bond interface:
1423
1424 1. Remove all VLAN interfaces then recreate them
1425
1426 2. Set the bonding interface's hardware address so that it
1427matches the hardware address of the VLAN interfaces.
1428
1429 Note that changing a VLAN interface's HW address would set the
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001430underlying device -- i.e. the bonding interface -- to promiscuous
Linus Torvalds1da177e2005-04-16 15:20:36 -07001431mode, which might not be what you want.
1432
1433
Auke Kok6224e012006-06-08 11:15:35 -070014347. Link Monitoring
Linus Torvalds1da177e2005-04-16 15:20:36 -07001435==================
1436
1437 The bonding driver at present supports two schemes for
1438monitoring a slave device's link state: the ARP monitor and the MII
1439monitor.
1440
1441 At the present time, due to implementation restrictions in the
1442bonding driver itself, it is not possible to enable both ARP and MII
1443monitoring simultaneously.
1444
Auke Kok6224e012006-06-08 11:15:35 -070014457.1 ARP Monitor Operation
Linus Torvalds1da177e2005-04-16 15:20:36 -07001446-------------------------
1447
1448 The ARP monitor operates as its name suggests: it sends ARP
1449queries to one or more designated peer systems on the network, and
1450uses the response as an indication that the link is operating. This
1451gives some assurance that traffic is actually flowing to and from one
1452or more peers on the local network.
1453
1454 The ARP monitor relies on the device driver itself to verify
1455that traffic is flowing. In particular, the driver must keep up to
1456date the last receive time, dev->last_rx, and transmit start time,
1457dev->trans_start. If these are not updated by the driver, then the
1458ARP monitor will immediately fail any slaves using that driver, and
1459those slaves will stay down. If networking monitoring (tcpdump, etc)
1460shows the ARP requests and replies on the network, then it may be that
1461your device driver is not updating last_rx and trans_start.
1462
Auke Kok6224e012006-06-08 11:15:35 -070014637.2 Configuring Multiple ARP Targets
Linus Torvalds1da177e2005-04-16 15:20:36 -07001464------------------------------------
1465
1466 While ARP monitoring can be done with just one target, it can
1467be useful in a High Availability setup to have several targets to
1468monitor. In the case of just one target, the target itself may go
1469down or have a problem making it unresponsive to ARP requests. Having
1470an additional target (or several) increases the reliability of the ARP
1471monitoring.
1472
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001473 Multiple ARP targets must be separated by commas as follows:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001474
1475# example options for ARP monitoring with three targets
1476alias bond0 bonding
1477options bond0 arp_interval=60 arp_ip_target=192.168.0.1,192.168.0.3,192.168.0.9
1478
1479 For just a single target the options would resemble:
1480
1481# example options for ARP monitoring with one target
1482alias bond0 bonding
1483options bond0 arp_interval=60 arp_ip_target=192.168.0.100
1484
1485
Auke Kok6224e012006-06-08 11:15:35 -070014867.3 MII Monitor Operation
Linus Torvalds1da177e2005-04-16 15:20:36 -07001487-------------------------
1488
1489 The MII monitor monitors only the carrier state of the local
1490network interface. It accomplishes this in one of three ways: by
1491depending upon the device driver to maintain its carrier state, by
1492querying the device's MII registers, or by making an ethtool query to
1493the device.
1494
1495 If the use_carrier module parameter is 1 (the default value),
1496then the MII monitor will rely on the driver for carrier state
1497information (via the netif_carrier subsystem). As explained in the
1498use_carrier parameter information, above, if the MII monitor fails to
1499detect carrier loss on the device (e.g., when the cable is physically
1500disconnected), it may be that the driver does not support
1501netif_carrier.
1502
1503 If use_carrier is 0, then the MII monitor will first query the
1504device's (via ioctl) MII registers and check the link state. If that
1505request fails (not just that it returns carrier down), then the MII
1506monitor will make an ethtool ETHOOL_GLINK request to attempt to obtain
1507the same information. If both methods fail (i.e., the driver either
1508does not support or had some error in processing both the MII register
1509and ethtool requests), then the MII monitor will assume the link is
1510up.
1511
Auke Kok6224e012006-06-08 11:15:35 -070015128. Potential Sources of Trouble
Linus Torvalds1da177e2005-04-16 15:20:36 -07001513===============================
1514
Auke Kok6224e012006-06-08 11:15:35 -070015158.1 Adventures in Routing
Linus Torvalds1da177e2005-04-16 15:20:36 -07001516-------------------------
1517
1518 When bonding is configured, it is important that the slave
Auke Kok6224e012006-06-08 11:15:35 -07001519devices not have routes that supersede routes of the master (or,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001520generally, not have routes at all). For example, suppose the bonding
1521device bond0 has two slaves, eth0 and eth1, and the routing table is
1522as follows:
1523
1524Kernel IP routing table
1525Destination Gateway Genmask Flags MSS Window irtt Iface
152610.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth0
152710.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth1
152810.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 bond0
1529127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo
1530
1531 This routing configuration will likely still update the
1532receive/transmit times in the driver (needed by the ARP monitor), but
1533may bypass the bonding driver (because outgoing traffic to, in this
1534case, another host on network 10 would use eth0 or eth1 before bond0).
1535
1536 The ARP monitor (and ARP itself) may become confused by this
1537configuration, because ARP requests (generated by the ARP monitor)
1538will be sent on one interface (bond0), but the corresponding reply
1539will arrive on a different interface (eth0). This reply looks to ARP
1540as an unsolicited ARP reply (because ARP matches replies on an
1541interface basis), and is discarded. The MII monitor is not affected
1542by the state of the routing table.
1543
1544 The solution here is simply to insure that slaves do not have
1545routes of their own, and if for some reason they must, those routes do
Auke Kok6224e012006-06-08 11:15:35 -07001546not supersede routes of their master. This should generally be the
Linus Torvalds1da177e2005-04-16 15:20:36 -07001547case, but unusual configurations or errant manual or automatic static
1548route additions may cause trouble.
1549
Auke Kok6224e012006-06-08 11:15:35 -070015508.2 Ethernet Device Renaming
Linus Torvalds1da177e2005-04-16 15:20:36 -07001551----------------------------
1552
1553 On systems with network configuration scripts that do not
1554associate physical devices directly with network interface names (so
1555that the same physical device always has the same "ethX" name), it may
1556be necessary to add some special logic to either /etc/modules.conf or
1557/etc/modprobe.conf (depending upon which is installed on the system).
1558
1559 For example, given a modules.conf containing the following:
1560
1561alias bond0 bonding
1562options bond0 mode=some-mode miimon=50
1563alias eth0 tg3
1564alias eth1 tg3
1565alias eth2 e1000
1566alias eth3 e1000
1567
1568 If neither eth0 and eth1 are slaves to bond0, then when the
1569bond0 interface comes up, the devices may end up reordered. This
1570happens because bonding is loaded first, then its slave device's
1571drivers are loaded next. Since no other drivers have been loaded,
1572when the e1000 driver loads, it will receive eth0 and eth1 for its
1573devices, but the bonding configuration tries to enslave eth2 and eth3
1574(which may later be assigned to the tg3 devices).
1575
1576 Adding the following:
1577
1578add above bonding e1000 tg3
1579
1580 causes modprobe to load e1000 then tg3, in that order, when
1581bonding is loaded. This command is fully documented in the
1582modules.conf manual page.
1583
1584 On systems utilizing modprobe.conf (or modprobe.conf.local),
1585an equivalent problem can occur. In this case, the following can be
1586added to modprobe.conf (or modprobe.conf.local, as appropriate), as
1587follows (all on one line; it has been split here for clarity):
1588
1589install bonding /sbin/modprobe tg3; /sbin/modprobe e1000;
1590 /sbin/modprobe --ignore-install bonding
1591
1592 This will, when loading the bonding module, rather than
1593performing the normal action, instead execute the provided command.
1594This command loads the device drivers in the order needed, then calls
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001595modprobe with --ignore-install to cause the normal action to then take
Linus Torvalds1da177e2005-04-16 15:20:36 -07001596place. Full documentation on this can be found in the modprobe.conf
1597and modprobe manual pages.
1598
Auke Kok6224e012006-06-08 11:15:35 -070015998.3. Painfully Slow Or No Failed Link Detection By Miimon
Linus Torvalds1da177e2005-04-16 15:20:36 -07001600---------------------------------------------------------
1601
1602 By default, bonding enables the use_carrier option, which
1603instructs bonding to trust the driver to maintain carrier state.
1604
1605 As discussed in the options section, above, some drivers do
1606not support the netif_carrier_on/_off link state tracking system.
1607With use_carrier enabled, bonding will always see these links as up,
1608regardless of their actual state.
1609
1610 Additionally, other drivers do support netif_carrier, but do
1611not maintain it in real time, e.g., only polling the link state at
1612some fixed interval. In this case, miimon will detect failures, but
1613only after some long period of time has expired. If it appears that
1614miimon is very slow in detecting link failures, try specifying
1615use_carrier=0 to see if that improves the failure detection time. If
1616it does, then it may be that the driver checks the carrier state at a
1617fixed interval, but does not cache the MII register values (so the
1618use_carrier=0 method of querying the registers directly works). If
1619use_carrier=0 does not improve the failover, then the driver may cache
1620the registers, or the problem may be elsewhere.
1621
1622 Also, remember that miimon only checks for the device's
1623carrier state. It has no way to determine the state of devices on or
1624beyond other ports of a switch, or if a switch is refusing to pass
1625traffic while still maintaining carrier on.
1626
Auke Kok6224e012006-06-08 11:15:35 -070016279. SNMP agents
Linus Torvalds1da177e2005-04-16 15:20:36 -07001628===============
1629
1630 If running SNMP agents, the bonding driver should be loaded
1631before any network drivers participating in a bond. This requirement
Tobias Klauserd533f672005-09-10 00:26:46 -07001632is due to the interface index (ipAdEntIfIndex) being associated to
Linus Torvalds1da177e2005-04-16 15:20:36 -07001633the first interface found with a given IP address. That is, there is
1634only one ipAdEntIfIndex for each IP address. For example, if eth0 and
1635eth1 are slaves of bond0 and the driver for eth0 is loaded before the
1636bonding driver, the interface for the IP address will be associated
1637with the eth0 interface. This configuration is shown below, the IP
1638address 192.168.1.1 has an interface index of 2 which indexes to eth0
1639in the ifDescr table (ifDescr.2).
1640
1641 interfaces.ifTable.ifEntry.ifDescr.1 = lo
1642 interfaces.ifTable.ifEntry.ifDescr.2 = eth0
1643 interfaces.ifTable.ifEntry.ifDescr.3 = eth1
1644 interfaces.ifTable.ifEntry.ifDescr.4 = eth2
1645 interfaces.ifTable.ifEntry.ifDescr.5 = eth3
1646 interfaces.ifTable.ifEntry.ifDescr.6 = bond0
1647 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 5
1648 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2
1649 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 4
1650 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
1651
1652 This problem is avoided by loading the bonding driver before
1653any network drivers participating in a bond. Below is an example of
1654loading the bonding driver first, the IP address 192.168.1.1 is
1655correctly associated with ifDescr.2.
1656
1657 interfaces.ifTable.ifEntry.ifDescr.1 = lo
1658 interfaces.ifTable.ifEntry.ifDescr.2 = bond0
1659 interfaces.ifTable.ifEntry.ifDescr.3 = eth0
1660 interfaces.ifTable.ifEntry.ifDescr.4 = eth1
1661 interfaces.ifTable.ifEntry.ifDescr.5 = eth2
1662 interfaces.ifTable.ifEntry.ifDescr.6 = eth3
1663 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 6
1664 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2
1665 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 5
1666 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
1667
1668 While some distributions may not report the interface name in
1669ifDescr, the association between the IP address and IfIndex remains
1670and SNMP functions such as Interface_Scan_Next will report that
1671association.
1672
Auke Kok6224e012006-06-08 11:15:35 -0700167310. Promiscuous mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07001674====================
1675
1676 When running network monitoring tools, e.g., tcpdump, it is
1677common to enable promiscuous mode on the device, so that all traffic
1678is seen (instead of seeing only traffic destined for the local host).
1679The bonding driver handles promiscuous mode changes to the bonding
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001680master device (e.g., bond0), and propagates the setting to the slave
Linus Torvalds1da177e2005-04-16 15:20:36 -07001681devices.
1682
1683 For the balance-rr, balance-xor, broadcast, and 802.3ad modes,
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001684the promiscuous mode setting is propagated to all slaves.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001685
1686 For the active-backup, balance-tlb and balance-alb modes, the
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001687promiscuous mode setting is propagated only to the active slave.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001688
1689 For balance-tlb mode, the active slave is the slave currently
1690receiving inbound traffic.
1691
1692 For balance-alb mode, the active slave is the slave used as a
1693"primary." This slave is used for mode-specific control traffic, for
1694sending to peers that are unassigned or if the load is unbalanced.
1695
1696 For the active-backup, balance-tlb and balance-alb modes, when
1697the active slave changes (e.g., due to a link failure), the
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001698promiscuous setting will be propagated to the new active slave.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001699
Auke Kok6224e012006-06-08 11:15:35 -0700170011. Configuring Bonding for High Availability
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001701=============================================
Linus Torvalds1da177e2005-04-16 15:20:36 -07001702
1703 High Availability refers to configurations that provide
1704maximum network availability by having redundant or backup devices,
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001705links or switches between the host and the rest of the world. The
1706goal is to provide the maximum availability of network connectivity
1707(i.e., the network always works), even though other configurations
1708could provide higher throughput.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001709
Auke Kok6224e012006-06-08 11:15:35 -0700171011.1 High Availability in a Single Switch Topology
Linus Torvalds1da177e2005-04-16 15:20:36 -07001711--------------------------------------------------
1712
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001713 If two hosts (or a host and a single switch) are directly
1714connected via multiple physical links, then there is no availability
1715penalty to optimizing for maximum bandwidth. In this case, there is
1716only one switch (or peer), so if it fails, there is no alternative
1717access to fail over to. Additionally, the bonding load balance modes
1718support link monitoring of their members, so if individual links fail,
1719the load will be rebalanced across the remaining devices.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001720
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001721 See Section 13, "Configuring Bonding for Maximum Throughput"
1722for information on configuring bonding with one peer device.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001723
Auke Kok6224e012006-06-08 11:15:35 -0700172411.2 High Availability in a Multiple Switch Topology
Linus Torvalds1da177e2005-04-16 15:20:36 -07001725----------------------------------------------------
1726
1727 With multiple switches, the configuration of bonding and the
1728network changes dramatically. In multiple switch topologies, there is
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001729a trade off between network availability and usable bandwidth.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001730
1731 Below is a sample network, configured to maximize the
1732availability of the network:
1733
1734 | |
1735 |port3 port3|
1736 +-----+----+ +-----+----+
1737 | |port2 ISL port2| |
1738 | switch A +--------------------------+ switch B |
1739 | | | |
1740 +-----+----+ +-----++---+
1741 |port1 port1|
1742 | +-------+ |
1743 +-------------+ host1 +---------------+
1744 eth0 +-------+ eth1
1745
1746 In this configuration, there is a link between the two
1747switches (ISL, or inter switch link), and multiple ports connecting to
1748the outside world ("port3" on each switch). There is no technical
1749reason that this could not be extended to a third switch.
1750
Auke Kok6224e012006-06-08 11:15:35 -0700175111.2.1 HA Bonding Mode Selection for Multiple Switch Topology
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001752-------------------------------------------------------------
Linus Torvalds1da177e2005-04-16 15:20:36 -07001753
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001754 In a topology such as the example above, the active-backup and
1755broadcast modes are the only useful bonding modes when optimizing for
1756availability; the other modes require all links to terminate on the
1757same peer for them to behave rationally.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001758
1759active-backup: This is generally the preferred mode, particularly if
1760 the switches have an ISL and play together well. If the
1761 network configuration is such that one switch is specifically
1762 a backup switch (e.g., has lower capacity, higher cost, etc),
1763 then the primary option can be used to insure that the
1764 preferred link is always used when it is available.
1765
1766broadcast: This mode is really a special purpose mode, and is suitable
1767 only for very specific needs. For example, if the two
1768 switches are not connected (no ISL), and the networks beyond
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001769 them are totally independent. In this case, if it is
Linus Torvalds1da177e2005-04-16 15:20:36 -07001770 necessary for some specific one-way traffic to reach both
1771 independent networks, then the broadcast mode may be suitable.
1772
Auke Kok6224e012006-06-08 11:15:35 -0700177311.2.2 HA Link Monitoring Selection for Multiple Switch Topology
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001774----------------------------------------------------------------
Linus Torvalds1da177e2005-04-16 15:20:36 -07001775
1776 The choice of link monitoring ultimately depends upon your
1777switch. If the switch can reliably fail ports in response to other
1778failures, then either the MII or ARP monitors should work. For
1779example, in the above example, if the "port3" link fails at the remote
1780end, the MII monitor has no direct means to detect this. The ARP
1781monitor could be configured with a target at the remote end of port3,
1782thus detecting that failure without switch support.
1783
1784 In general, however, in a multiple switch topology, the ARP
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001785monitor can provide a higher level of reliability in detecting end to
1786end connectivity failures (which may be caused by the failure of any
1787individual component to pass traffic for any reason). Additionally,
1788the ARP monitor should be configured with multiple targets (at least
1789one for each switch in the network). This will insure that,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001790regardless of which switch is active, the ARP monitor has a suitable
1791target to query.
1792
Jay Vosburgh9a6c6862007-11-13 20:25:48 -08001793 Note, also, that of late many switches now support a functionality
1794generally referred to as "trunk failover." This is a feature of the
1795switch that causes the link state of a particular switch port to be set
1796down (or up) when the state of another switch port goes down (or up).
1797It's purpose is to propogate link failures from logically "exterior" ports
1798to the logically "interior" ports that bonding is able to monitor via
1799miimon. Availability and configuration for trunk failover varies by
1800switch, but this can be a viable alternative to the ARP monitor when using
1801suitable switches.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001802
Auke Kok6224e012006-06-08 11:15:35 -0700180312. Configuring Bonding for Maximum Throughput
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001804==============================================
Linus Torvalds1da177e2005-04-16 15:20:36 -07001805
Auke Kok6224e012006-06-08 11:15:35 -0700180612.1 Maximizing Throughput in a Single Switch Topology
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001807------------------------------------------------------
1808
1809 In a single switch configuration, the best method to maximize
1810throughput depends upon the application and network environment. The
1811various load balancing modes each have strengths and weaknesses in
1812different environments, as detailed below.
1813
1814 For this discussion, we will break down the topologies into
1815two categories. Depending upon the destination of most traffic, we
1816categorize them into either "gatewayed" or "local" configurations.
1817
1818 In a gatewayed configuration, the "switch" is acting primarily
1819as a router, and the majority of traffic passes through this router to
1820other networks. An example would be the following:
1821
1822
1823 +----------+ +----------+
1824 | |eth0 port1| | to other networks
1825 | Host A +---------------------+ router +------------------->
1826 | +---------------------+ | Hosts B and C are out
1827 | |eth1 port2| | here somewhere
1828 +----------+ +----------+
1829
1830 The router may be a dedicated router device, or another host
1831acting as a gateway. For our discussion, the important point is that
1832the majority of traffic from Host A will pass through the router to
1833some other network before reaching its final destination.
1834
1835 In a gatewayed network configuration, although Host A may
1836communicate with many other systems, all of its traffic will be sent
1837and received via one other peer on the local network, the router.
1838
1839 Note that the case of two systems connected directly via
1840multiple physical links is, for purposes of configuring bonding, the
1841same as a gatewayed configuration. In that case, it happens that all
1842traffic is destined for the "gateway" itself, not some other network
1843beyond the gateway.
1844
1845 In a local configuration, the "switch" is acting primarily as
1846a switch, and the majority of traffic passes through this switch to
1847reach other stations on the same network. An example would be the
1848following:
1849
1850 +----------+ +----------+ +--------+
1851 | |eth0 port1| +-------+ Host B |
1852 | Host A +------------+ switch |port3 +--------+
1853 | +------------+ | +--------+
1854 | |eth1 port2| +------------------+ Host C |
1855 +----------+ +----------+port4 +--------+
1856
1857
1858 Again, the switch may be a dedicated switch device, or another
1859host acting as a gateway. For our discussion, the important point is
1860that the majority of traffic from Host A is destined for other hosts
1861on the same local network (Hosts B and C in the above example).
1862
1863 In summary, in a gatewayed configuration, traffic to and from
1864the bonded device will be to the same MAC level peer on the network
1865(the gateway itself, i.e., the router), regardless of its final
1866destination. In a local configuration, traffic flows directly to and
1867from the final destinations, thus, each destination (Host B, Host C)
1868will be addressed directly by their individual MAC addresses.
1869
1870 This distinction between a gatewayed and a local network
1871configuration is important because many of the load balancing modes
1872available use the MAC addresses of the local network source and
1873destination to make load balancing decisions. The behavior of each
1874mode is described below.
1875
1876
Auke Kok6224e012006-06-08 11:15:35 -0700187712.1.1 MT Bonding Mode Selection for Single Switch Topology
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001878-----------------------------------------------------------
1879
1880 This configuration is the easiest to set up and to understand,
1881although you will have to decide which bonding mode best suits your
1882needs. The trade offs for each mode are detailed below:
1883
1884balance-rr: This mode is the only mode that will permit a single
1885 TCP/IP connection to stripe traffic across multiple
1886 interfaces. It is therefore the only mode that will allow a
1887 single TCP/IP stream to utilize more than one interface's
1888 worth of throughput. This comes at a cost, however: the
Jay Vosburgh9a6c6862007-11-13 20:25:48 -08001889 striping generally results in peer systems receiving packets out
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001890 of order, causing TCP/IP's congestion control system to kick
1891 in, often by retransmitting segments.
1892
1893 It is possible to adjust TCP/IP's congestion limits by
1894 altering the net.ipv4.tcp_reordering sysctl parameter. The
1895 usual default value is 3, and the maximum useful value is 127.
1896 For a four interface balance-rr bond, expect that a single
1897 TCP/IP stream will utilize no more than approximately 2.3
1898 interface's worth of throughput, even after adjusting
1899 tcp_reordering.
1900
Jay Vosburgh9a6c6862007-11-13 20:25:48 -08001901 Note that the fraction of packets that will be delivered out of
1902 order is highly variable, and is unlikely to be zero. The level
1903 of reordering depends upon a variety of factors, including the
1904 networking interfaces, the switch, and the topology of the
1905 configuration. Speaking in general terms, higher speed network
1906 cards produce more reordering (due to factors such as packet
1907 coalescing), and a "many to many" topology will reorder at a
1908 higher rate than a "many slow to one fast" configuration.
1909
1910 Many switches do not support any modes that stripe traffic
1911 (instead choosing a port based upon IP or MAC level addresses);
1912 for those devices, traffic for a particular connection flowing
1913 through the switch to a balance-rr bond will not utilize greater
1914 than one interface's worth of bandwidth.
Jay Vosburgh00354cf2005-07-21 12:18:02 -07001915
1916 If you are utilizing protocols other than TCP/IP, UDP for
1917 example, and your application can tolerate out of order
1918 delivery, then this mode can allow for single stream datagram
1919 performance that scales near linearly as interfaces are added
1920 to the bond.
1921
1922 This mode requires the switch to have the appropriate ports
1923 configured for "etherchannel" or "trunking."
1924
1925active-backup: There is not much advantage in this network topology to
1926 the active-backup mode, as the inactive backup devices are all
1927 connected to the same peer as the primary. In this case, a
1928 load balancing mode (with link monitoring) will provide the
1929 same level of network availability, but with increased
1930 available bandwidth. On the plus side, active-backup mode
1931 does not require any configuration of the switch, so it may
1932 have value if the hardware available does not support any of
1933 the load balance modes.
1934
1935balance-xor: This mode will limit traffic such that packets destined
1936 for specific peers will always be sent over the same
1937 interface. Since the destination is determined by the MAC
1938 addresses involved, this mode works best in a "local" network
1939 configuration (as described above), with destinations all on
1940 the same local network. This mode is likely to be suboptimal
1941 if all your traffic is passed through a single router (i.e., a
1942 "gatewayed" network configuration, as described above).
1943
1944 As with balance-rr, the switch ports need to be configured for
1945 "etherchannel" or "trunking."
1946
1947broadcast: Like active-backup, there is not much advantage to this
1948 mode in this type of network topology.
1949
1950802.3ad: This mode can be a good choice for this type of network
1951 topology. The 802.3ad mode is an IEEE standard, so all peers
1952 that implement 802.3ad should interoperate well. The 802.3ad
1953 protocol includes automatic configuration of the aggregates,
1954 so minimal manual configuration of the switch is needed
1955 (typically only to designate that some set of devices is
1956 available for 802.3ad). The 802.3ad standard also mandates
1957 that frames be delivered in order (within certain limits), so
1958 in general single connections will not see misordering of
1959 packets. The 802.3ad mode does have some drawbacks: the
1960 standard mandates that all devices in the aggregate operate at
1961 the same speed and duplex. Also, as with all bonding load
1962 balance modes other than balance-rr, no single connection will
1963 be able to utilize more than a single interface's worth of
1964 bandwidth.
1965
1966 Additionally, the linux bonding 802.3ad implementation
1967 distributes traffic by peer (using an XOR of MAC addresses),
1968 so in a "gatewayed" configuration, all outgoing traffic will
1969 generally use the same device. Incoming traffic may also end
1970 up on a single device, but that is dependent upon the
1971 balancing policy of the peer's 8023.ad implementation. In a
1972 "local" configuration, traffic will be distributed across the
1973 devices in the bond.
1974
1975 Finally, the 802.3ad mode mandates the use of the MII monitor,
1976 therefore, the ARP monitor is not available in this mode.
1977
1978balance-tlb: The balance-tlb mode balances outgoing traffic by peer.
1979 Since the balancing is done according to MAC address, in a
1980 "gatewayed" configuration (as described above), this mode will
1981 send all traffic across a single device. However, in a
1982 "local" network configuration, this mode balances multiple
1983 local network peers across devices in a vaguely intelligent
1984 manner (not a simple XOR as in balance-xor or 802.3ad mode),
1985 so that mathematically unlucky MAC addresses (i.e., ones that
1986 XOR to the same value) will not all "bunch up" on a single
1987 interface.
1988
1989 Unlike 802.3ad, interfaces may be of differing speeds, and no
1990 special switch configuration is required. On the down side,
1991 in this mode all incoming traffic arrives over a single
1992 interface, this mode requires certain ethtool support in the
1993 network device driver of the slave interfaces, and the ARP
1994 monitor is not available.
1995
1996balance-alb: This mode is everything that balance-tlb is, and more.
1997 It has all of the features (and restrictions) of balance-tlb,
1998 and will also balance incoming traffic from local network
1999 peers (as described in the Bonding Module Options section,
2000 above).
2001
2002 The only additional down side to this mode is that the network
2003 device driver must support changing the hardware address while
2004 the device is open.
2005
Auke Kok6224e012006-06-08 11:15:35 -0700200612.1.2 MT Link Monitoring for Single Switch Topology
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002007----------------------------------------------------
2008
2009 The choice of link monitoring may largely depend upon which
2010mode you choose to use. The more advanced load balancing modes do not
2011support the use of the ARP monitor, and are thus restricted to using
2012the MII monitor (which does not provide as high a level of end to end
2013assurance as the ARP monitor).
2014
Auke Kok6224e012006-06-08 11:15:35 -0700201512.2 Maximum Throughput in a Multiple Switch Topology
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002016-----------------------------------------------------
2017
2018 Multiple switches may be utilized to optimize for throughput
2019when they are configured in parallel as part of an isolated network
2020between two or more systems, for example:
2021
2022 +-----------+
2023 | Host A |
2024 +-+---+---+-+
2025 | | |
2026 +--------+ | +---------+
2027 | | |
2028 +------+---+ +-----+----+ +-----+----+
2029 | Switch A | | Switch B | | Switch C |
2030 +------+---+ +-----+----+ +-----+----+
2031 | | |
2032 +--------+ | +---------+
2033 | | |
2034 +-+---+---+-+
2035 | Host B |
2036 +-----------+
2037
2038 In this configuration, the switches are isolated from one
2039another. One reason to employ a topology such as this is for an
2040isolated network with many hosts (a cluster configured for high
2041performance, for example), using multiple smaller switches can be more
2042cost effective than a single larger switch, e.g., on a network with 24
2043hosts, three 24 port switches can be significantly less expensive than
2044a single 72 port switch.
2045
2046 If access beyond the network is required, an individual host
2047can be equipped with an additional network device connected to an
2048external network; this host then additionally acts as a gateway.
2049
Auke Kok6224e012006-06-08 11:15:35 -0700205012.2.1 MT Bonding Mode Selection for Multiple Switch Topology
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002051-------------------------------------------------------------
2052
2053 In actual practice, the bonding mode typically employed in
2054configurations of this type is balance-rr. Historically, in this
2055network configuration, the usual caveats about out of order packet
2056delivery are mitigated by the use of network adapters that do not do
2057any kind of packet coalescing (via the use of NAPI, or because the
2058device itself does not generate interrupts until some number of
2059packets has arrived). When employed in this fashion, the balance-rr
2060mode allows individual connections between two hosts to effectively
2061utilize greater than one interface's bandwidth.
2062
Auke Kok6224e012006-06-08 11:15:35 -0700206312.2.2 MT Link Monitoring for Multiple Switch Topology
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002064------------------------------------------------------
2065
2066 Again, in actual practice, the MII monitor is most often used
2067in this configuration, as performance is given preference over
2068availability. The ARP monitor will function in this topology, but its
2069advantages over the MII monitor are mitigated by the volume of probes
2070needed as the number of systems involved grows (remember that each
2071host in the network is configured with bonding).
2072
Auke Kok6224e012006-06-08 11:15:35 -0700207313. Switch Behavior Issues
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002074==========================
2075
Auke Kok6224e012006-06-08 11:15:35 -0700207613.1 Link Establishment and Failover Delays
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002077-------------------------------------------
2078
2079 Some switches exhibit undesirable behavior with regard to the
2080timing of link up and down reporting by the switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002081
2082 First, when a link comes up, some switches may indicate that
2083the link is up (carrier available), but not pass traffic over the
2084interface for some period of time. This delay is typically due to
2085some type of autonegotiation or routing protocol, but may also occur
2086during switch initialization (e.g., during recovery after a switch
2087failure). If you find this to be a problem, specify an appropriate
2088value to the updelay bonding module option to delay the use of the
2089relevant interface(s).
2090
2091 Second, some switches may "bounce" the link state one or more
2092times while a link is changing state. This occurs most commonly while
2093the switch is initializing. Again, an appropriate updelay value may
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002094help.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002095
2096 Note that when a bonding interface has no active links, the
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002097driver will immediately reuse the first link that goes up, even if the
2098updelay parameter has been specified (the updelay is ignored in this
2099case). If there are slave interfaces waiting for the updelay timeout
2100to expire, the interface that first went into that state will be
2101immediately reused. This reduces down time of the network if the
2102value of updelay has been overestimated, and since this occurs only in
2103cases with no connectivity, there is no additional penalty for
2104ignoring the updelay.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002105
2106 In addition to the concerns about switch timings, if your
2107switches take a long time to go into backup mode, it may be desirable
2108to not activate a backup interface immediately after a link goes down.
2109Failover may be delayed via the downdelay bonding module option.
2110
Auke Kok6224e012006-06-08 11:15:35 -0700211113.2 Duplicated Incoming Packets
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002112--------------------------------
2113
Jay Vosburgh9a6c6862007-11-13 20:25:48 -08002114 NOTE: Starting with version 3.0.2, the bonding driver has logic to
2115suppress duplicate packets, which should largely eliminate this problem.
2116The following description is kept for reference.
2117
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002118 It is not uncommon to observe a short burst of duplicated
2119traffic when the bonding device is first used, or after it has been
2120idle for some period of time. This is most easily observed by issuing
2121a "ping" to some other host on the network, and noticing that the
2122output from ping flags duplicates (typically one per slave).
2123
2124 For example, on a bond in active-backup mode with five slaves
2125all connected to one switch, the output may appear as follows:
2126
2127# ping -n 10.0.4.2
2128PING 10.0.4.2 (10.0.4.2) from 10.0.3.10 : 56(84) bytes of data.
212964 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.7 ms
213064 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
213164 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
213264 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
213364 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
213464 bytes from 10.0.4.2: icmp_seq=2 ttl=64 time=0.216 ms
213564 bytes from 10.0.4.2: icmp_seq=3 ttl=64 time=0.267 ms
213664 bytes from 10.0.4.2: icmp_seq=4 ttl=64 time=0.222 ms
2137
2138 This is not due to an error in the bonding driver, rather, it
2139is a side effect of how many switches update their MAC forwarding
2140tables. Initially, the switch does not associate the MAC address in
2141the packet with a particular switch port, and so it may send the
2142traffic to all ports until its MAC forwarding table is updated. Since
2143the interfaces attached to the bond may occupy multiple ports on a
2144single switch, when the switch (temporarily) floods the traffic to all
2145ports, the bond device receives multiple copies of the same packet
2146(one per slave device).
2147
2148 The duplicated packet behavior is switch dependent, some
2149switches exhibit this, and some do not. On switches that display this
2150behavior, it can be induced by clearing the MAC forwarding table (on
2151most Cisco switches, the privileged command "clear mac address-table
2152dynamic" will accomplish this).
2153
Auke Kok6224e012006-06-08 11:15:35 -0700215414. Hardware Specific Considerations
Linus Torvalds1da177e2005-04-16 15:20:36 -07002155====================================
2156
2157 This section contains additional information for configuring
2158bonding on specific hardware platforms, or for interfacing bonding
2159with particular switches or other devices.
2160
Auke Kok6224e012006-06-08 11:15:35 -0700216114.1 IBM BladeCenter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002162--------------------
2163
2164 This applies to the JS20 and similar systems.
2165
2166 On the JS20 blades, the bonding driver supports only
2167balance-rr, active-backup, balance-tlb and balance-alb modes. This is
2168largely due to the network topology inside the BladeCenter, detailed
2169below.
2170
2171JS20 network adapter information
2172--------------------------------
2173
2174 All JS20s come with two Broadcom Gigabit Ethernet ports
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002175integrated on the planar (that's "motherboard" in IBM-speak). In the
2176BladeCenter chassis, the eth0 port of all JS20 blades is hard wired to
2177I/O Module #1; similarly, all eth1 ports are wired to I/O Module #2.
2178An add-on Broadcom daughter card can be installed on a JS20 to provide
2179two more Gigabit Ethernet ports. These ports, eth2 and eth3, are
2180wired to I/O Modules 3 and 4, respectively.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002181
2182 Each I/O Module may contain either a switch or a passthrough
2183module (which allows ports to be directly connected to an external
2184switch). Some bonding modes require a specific BladeCenter internal
2185network topology in order to function; these are detailed below.
2186
2187 Additional BladeCenter-specific networking information can be
2188found in two IBM Redbooks (www.ibm.com/redbooks):
2189
2190"IBM eServer BladeCenter Networking Options"
2191"IBM eServer BladeCenter Layer 2-7 Network Switching"
2192
2193BladeCenter networking configuration
2194------------------------------------
2195
2196 Because a BladeCenter can be configured in a very large number
2197of ways, this discussion will be confined to describing basic
2198configurations.
2199
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002200 Normally, Ethernet Switch Modules (ESMs) are used in I/O
Linus Torvalds1da177e2005-04-16 15:20:36 -07002201modules 1 and 2. In this configuration, the eth0 and eth1 ports of a
2202JS20 will be connected to different internal switches (in the
2203respective I/O modules).
2204
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002205 A passthrough module (OPM or CPM, optical or copper,
2206passthrough module) connects the I/O module directly to an external
2207switch. By using PMs in I/O module #1 and #2, the eth0 and eth1
2208interfaces of a JS20 can be redirected to the outside world and
2209connected to a common external switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002210
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002211 Depending upon the mix of ESMs and PMs, the network will
2212appear to bonding as either a single switch topology (all PMs) or as a
2213multiple switch topology (one or more ESMs, zero or more PMs). It is
2214also possible to connect ESMs together, resulting in a configuration
2215much like the example in "High Availability in a Multiple Switch
2216Topology," above.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002217
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002218Requirements for specific modes
2219-------------------------------
Linus Torvalds1da177e2005-04-16 15:20:36 -07002220
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002221 The balance-rr mode requires the use of passthrough modules
2222for devices in the bond, all connected to an common external switch.
2223That switch must be configured for "etherchannel" or "trunking" on the
Linus Torvalds1da177e2005-04-16 15:20:36 -07002224appropriate ports, as is usual for balance-rr.
2225
2226 The balance-alb and balance-tlb modes will function with
2227either switch modules or passthrough modules (or a mix). The only
2228specific requirement for these modes is that all network interfaces
2229must be able to reach all destinations for traffic sent over the
2230bonding device (i.e., the network must converge at some point outside
2231the BladeCenter).
2232
2233 The active-backup mode has no additional requirements.
2234
2235Link monitoring issues
2236----------------------
2237
2238 When an Ethernet Switch Module is in place, only the ARP
2239monitor will reliably detect link loss to an external switch. This is
2240nothing unusual, but examination of the BladeCenter cabinet would
2241suggest that the "external" network ports are the ethernet ports for
2242the system, when it fact there is a switch between these "external"
2243ports and the devices on the JS20 system itself. The MII monitor is
2244only able to detect link failures between the ESM and the JS20 system.
2245
2246 When a passthrough module is in place, the MII monitor does
2247detect failures to the "external" port, which is then directly
2248connected to the JS20 system.
2249
2250Other concerns
2251--------------
2252
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002253 The Serial Over LAN (SoL) link is established over the primary
Linus Torvalds1da177e2005-04-16 15:20:36 -07002254ethernet (eth0) only, therefore, any loss of link to eth0 will result
2255in losing your SoL connection. It will not fail over with other
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002256network traffic, as the SoL system is beyond the control of the
2257bonding driver.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002258
2259 It may be desirable to disable spanning tree on the switch
2260(either the internal Ethernet Switch Module, or an external switch) to
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002261avoid fail-over delay issues when using bonding.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002262
2263
Auke Kok6224e012006-06-08 11:15:35 -0700226415. Frequently Asked Questions
Linus Torvalds1da177e2005-04-16 15:20:36 -07002265==============================
2266
22671. Is it SMP safe?
2268
2269 Yes. The old 2.0.xx channel bonding patch was not SMP safe.
2270The new driver was designed to be SMP safe from the start.
2271
22722. What type of cards will work with it?
2273
2274 Any Ethernet type cards (you can even mix cards - a Intel
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002275EtherExpress PRO/100 and a 3com 3c905b, for example). For most modes,
2276devices need not be of the same speed.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002277
Jay Vosburgh9a6c6862007-11-13 20:25:48 -08002278 Starting with version 3.2.1, bonding also supports Infiniband
2279slaves in active-backup mode.
2280
Linus Torvalds1da177e2005-04-16 15:20:36 -070022813. How many bonding devices can I have?
2282
2283 There is no limit.
2284
22854. How many slaves can a bonding device have?
2286
2287 This is limited only by the number of network interfaces Linux
2288supports and/or the number of network cards you can place in your
2289system.
2290
22915. What happens when a slave link dies?
2292
2293 If link monitoring is enabled, then the failing device will be
2294disabled. The active-backup mode will fail over to a backup link, and
2295other modes will ignore the failed link. The link will continue to be
2296monitored, and should it recover, it will rejoin the bond (in whatever
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002297manner is appropriate for the mode). See the sections on High
2298Availability and the documentation for each mode for additional
2299information.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002300
2301 Link monitoring can be enabled via either the miimon or
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002302arp_interval parameters (described in the module parameters section,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002303above). In general, miimon monitors the carrier state as sensed by
2304the underlying network device, and the arp monitor (arp_interval)
2305monitors connectivity to another host on the local network.
2306
2307 If no link monitoring is configured, the bonding driver will
2308be unable to detect link failures, and will assume that all links are
2309always available. This will likely result in lost packets, and a
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002310resulting degradation of performance. The precise performance loss
Linus Torvalds1da177e2005-04-16 15:20:36 -07002311depends upon the bonding mode and network configuration.
2312
23136. Can bonding be used for High Availability?
2314
2315 Yes. See the section on High Availability for details.
2316
23177. Which switches/systems does it work with?
2318
2319 The full answer to this depends upon the desired mode.
2320
2321 In the basic balance modes (balance-rr and balance-xor), it
2322works with any system that supports etherchannel (also called
2323trunking). Most managed switches currently available have such
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002324support, and many unmanaged switches as well.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002325
2326 The advanced balance modes (balance-tlb and balance-alb) do
2327not have special switch requirements, but do need device drivers that
2328support specific features (described in the appropriate section under
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002329module parameters, above).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002330
Auke Kok6224e012006-06-08 11:15:35 -07002331 In 802.3ad mode, it works with systems that support IEEE
Linus Torvalds1da177e2005-04-16 15:20:36 -07002332802.3ad Dynamic Link Aggregation. Most managed and many unmanaged
2333switches currently available support 802.3ad.
2334
2335 The active-backup mode should work with any Layer-II switch.
2336
23378. Where does a bonding device get its MAC address from?
2338
Jay Vosburgh9a6c6862007-11-13 20:25:48 -08002339 When using slave devices that have fixed MAC addresses, or when
2340the fail_over_mac option is enabled, the bonding device's MAC address is
2341the MAC address of the active slave.
2342
2343 For other configurations, if not explicitly configured (with
2344ifconfig or ip link), the MAC address of the bonding device is taken from
2345its first slave device. This MAC address is then passed to all following
2346slaves and remains persistent (even if the first slave is removed) until
2347the bonding device is brought down or reconfigured.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002348
2349 If you wish to change the MAC address, you can set it with
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002350ifconfig or ip link:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002351
2352# ifconfig bond0 hw ether 00:11:22:33:44:55
2353
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002354# ip link set bond0 address 66:77:88:99:aa:bb
2355
Linus Torvalds1da177e2005-04-16 15:20:36 -07002356 The MAC address can be also changed by bringing down/up the
2357device and then changing its slaves (or their order):
2358
2359# ifconfig bond0 down ; modprobe -r bonding
2360# ifconfig bond0 .... up
2361# ifenslave bond0 eth...
2362
2363 This method will automatically take the address from the next
2364slave that is added.
2365
2366 To restore your slaves' MAC addresses, you need to detach them
2367from the bond (`ifenslave -d bond0 eth0'). The bonding driver will
2368then restore the MAC addresses that the slaves had before they were
2369enslaved.
2370
Jay Vosburgh00354cf2005-07-21 12:18:02 -0700237116. Resources and Links
Linus Torvalds1da177e2005-04-16 15:20:36 -07002372=======================
2373
2374The latest version of the bonding driver can be found in the latest
2375version of the linux kernel, found on http://kernel.org
2376
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002377The latest version of this document can be found in either the latest
2378kernel source (named Documentation/networking/bonding.txt), or on the
2379bonding sourceforge site:
2380
2381http://www.sourceforge.net/projects/bonding
2382
Linus Torvalds1da177e2005-04-16 15:20:36 -07002383Discussions regarding the bonding driver take place primarily on the
2384bonding-devel mailing list, hosted at sourceforge.net. If you have
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002385questions or problems, post them to the list. The list address is:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002386
2387bonding-devel@lists.sourceforge.net
2388
Jay Vosburgh00354cf2005-07-21 12:18:02 -07002389 The administrative interface (to subscribe or unsubscribe) can
2390be found at:
2391
Linus Torvalds1da177e2005-04-16 15:20:36 -07002392https://lists.sourceforge.net/lists/listinfo/bonding-devel
2393
Linus Torvalds1da177e2005-04-16 15:20:36 -07002394Donald Becker's Ethernet Drivers and diag programs may be found at :
2395 - http://www.scyld.com/network/
2396
2397You will also find a lot of information regarding Ethernet, NWay, MII,
2398etc. at www.scyld.com.
2399
2400-- END --