diff --git a/link_monitor.cc b/link_monitor.cc
index 1d8dd1b..26cb0dd 100644
--- a/link_monitor.cc
+++ b/link_monitor.cc
@@ -88,7 +88,7 @@
   timerclear(&sent_request_at_);
 }
 
-unsigned int LinkMonitor::GetResponseTimeMilliseconds() {
+unsigned int LinkMonitor::GetResponseTimeMilliseconds() const {
   return response_sample_count_ ?
       response_sample_bucket_ / response_sample_count_ : 0;
 }
@@ -125,6 +125,8 @@
   if (!arp_client_->Start()) {
     return false;
   }
+  SLOG(Link, 4) << "Created ARP client; listening on socket "
+                << arp_client_->socket() << ".";
   receive_response_handler_.reset(
     dispatcher_->CreateReadyHandler(
         arp_client_->socket(),
@@ -169,6 +171,10 @@
   return false;
 }
 
+bool LinkMonitor::IsGatewayFound() const {
+  return !gateway_mac_address_.IsZero();
+}
+
 void LinkMonitor::ReceiveResponse(int fd) {
   SLOG(Link, 2) << "In " << __func__ << ".";
   ArpPacket packet;
@@ -177,17 +183,19 @@
     return;
   }
 
-  if (!connection_->local().Equals(packet.local_ip_address())) {
+  if (!connection_->local().address().Equals(
+           packet.remote_ip_address().address())) {
     SLOG(Link, 4) << "Response is not for our IP address.";
     return;
   }
 
-  if (!local_mac_address_.Equals(packet.local_mac_address())) {
+  if (!local_mac_address_.Equals(packet.remote_mac_address())) {
     SLOG(Link, 4) << "Response is not for our MAC address.";
     return;
   }
 
-  if (!connection_->gateway().Equals(packet.remote_ip_address())) {
+  if (!connection_->gateway().address().Equals(
+           packet.local_ip_address().address())) {
     SLOG(Link, 4) << "Response is not from the gateway IP address.";
     return;
   }
@@ -208,9 +216,9 @@
     broadcast_failure_count_ = 0;
   }
 
-  if (!gateway_mac_address_.Equals(packet.remote_mac_address())) {
-    const ByteString &new_mac_address = packet.remote_mac_address();
-    if (gateway_mac_address_.IsZero()) {
+  if (!gateway_mac_address_.Equals(packet.local_mac_address())) {
+    const ByteString &new_mac_address = packet.local_mac_address();
+    if (!IsGatewayFound()) {
       SLOG(Link, 2) << "Found gateway at "
                     << HardwareAddressToString(new_mac_address);
     } else {
@@ -248,7 +256,7 @@
   }
 
   ByteString destination_mac_address(gateway_mac_address_.GetLength());
-  if (gateway_mac_address_.IsZero()) {
+  if (!IsGatewayFound()) {
     // The remote MAC addess is set by convention to be all-zeroes in the
     // ARP header if not known.  The ArpClient will translate an all-zeroes
     // remote address into a send to the broadcast (all-ones) address in
diff --git a/link_monitor.h b/link_monitor.h
index 60a4057..3a420cf 100644
--- a/link_monitor.h
+++ b/link_monitor.h
@@ -56,7 +56,11 @@
   // time.  Returns zero if no samples are available.  For each
   // missed ARP response, the sample is assumed to be the full
   // test period.
-  virtual unsigned int GetResponseTimeMilliseconds();
+  virtual unsigned int GetResponseTimeMilliseconds() const;
+
+  // Returns true if the LinkMonitor was ever able to find the default
+  // gateway via broadcast ARP.
+  virtual bool IsGatewayFound() const;
 
  private:
   friend class LinkMonitorForTest;
diff --git a/link_monitor_unittest.cc b/link_monitor_unittest.cc
index 27aaf52..de3dc61 100644
--- a/link_monitor_unittest.cc
+++ b/link_monitor_unittest.cc
@@ -221,7 +221,7 @@
     monitor_.ReceiveResponse(0);
   }
   void ReceiveCorrectResponse() {
-    ReceiveResponse(local_ip_, local_mac_, gateway_ip_, gateway_mac_);
+    ReceiveResponse(gateway_ip_, gateway_mac_, local_ip_, local_mac_);
   }
 
   MockEventDispatcher dispatcher_;
@@ -316,17 +316,17 @@
 
   EXPECT_CALL(log, Log(_, _, _)).Times(AnyNumber());
   EXPECT_CALL(log, Log(_, _, HasSubstr("not for our IP"))).Times(1);
-  ReceiveResponse(gateway_ip_, local_mac_, gateway_ip_, gateway_mac_);
+  ReceiveResponse(gateway_ip_, gateway_mac_, gateway_ip_, local_mac_);
   Mock::VerifyAndClearExpectations(&log);
 
   EXPECT_CALL(log, Log(_, _, _)).Times(AnyNumber());
   EXPECT_CALL(log, Log(_, _, HasSubstr("not for our MAC"))).Times(1);
-  ReceiveResponse(local_ip_, gateway_mac_, gateway_ip_, gateway_mac_);
+  ReceiveResponse(gateway_ip_, gateway_mac_, local_ip_, gateway_mac_);
   Mock::VerifyAndClearExpectations(&log);
 
   EXPECT_CALL(log, Log(_, _, _)).Times(AnyNumber());
   EXPECT_CALL(log, Log(_, _, HasSubstr("not from the gateway"))).Times(1);
-  ReceiveResponse(local_ip_, local_mac_, local_ip_, gateway_mac_);
+  ReceiveResponse(local_ip_, gateway_mac_, local_ip_, local_mac_);
   Mock::VerifyAndClearExpectations(&log);
 
   EXPECT_TRUE(GetArpClient());
diff --git a/mock_link_monitor.h b/mock_link_monitor.h
index 083b5d2..b76137d 100644
--- a/mock_link_monitor.h
+++ b/mock_link_monitor.h
@@ -18,7 +18,8 @@
 
   MOCK_METHOD0(Start, bool());
   MOCK_METHOD0(Stop, void());
-  MOCK_METHOD0(GetResponseTimeMilliseconds, unsigned int());
+  MOCK_CONST_METHOD0(GetResponseTimeMilliseconds, unsigned int());
+  MOCK_CONST_METHOD0(IsGatewayFound, bool());
 
   DISALLOW_COPY_AND_ASSIGN(MockLinkMonitor);
 };