| Allows you to restrict the number of parallel connections to a server per |
| client IP address (or client address block). |
| .TP |
| [\fB!\fP] \fB\-\-connlimit\-above\fP \fIn\fP |
| Match if the number of existing connections is (not) above \fIn\fR. |
| .TP |
| \fB\-\-connlimit\-mask\fP \fIprefix_length\fP |
| Group hosts using the prefix length. For IPv4, this must be a number between |
| (including) 0 and 32. For IPv6, between 0 and 128. |
| .P |
| Examples: |
| .TP |
| # allow 2 telnet connections per client host |
| iptables \-A INPUT \-p tcp \-\-syn \-\-dport 23 \-m connlimit \-\-connlimit\-above 2 \-j REJECT |
| .TP |
| # you can also match the other way around: |
| iptables \-A INPUT \-p tcp \-\-syn \-\-dport 23 \-m connlimit ! \-\-connlimit\-above 2 \-j ACCEPT |
| .TP |
| # limit the number of parallel HTTP requests to 16 per class C sized \ |
| network (24 bit netmask) |
| iptables \-p tcp \-\-syn \-\-dport 80 \-m connlimit \-\-connlimit\-above 16 |
| \-\-connlimit\-mask 24 \-j REJECT |
| .TP |
| # limit the number of parallel HTTP requests to 16 for the link local network \ |
| (ipv6) |
| ip6tables \-p tcp \-\-syn \-\-dport 80 \-s fe80::/64 \-m connlimit \-\-connlimit\-above |
| 16 \-\-connlimit\-mask 64 \-j REJECT |