Which is not particularly helpful when eth3 is connected to a different LAN with a router that actually checks the IP addresses of packets it forwards. At which point it eats the SSH connection I was using (because that was to an IP address on eth0) and I had to wander down to the lab and dig out a keyboard and monitor.
I am becoming more and more convinced that the Linux network stack just Does Not Work as soon as you plug it into more than one network.