Software :: How Is Localhost Tied To A Particular NIC

I've been involved in the setup of a 3 node cluster that uses multicast to communicate between them. Each of these 3 boxes are pretty much identical, network-wise, with 4 ethernet interfaces. Before configuring the cluster we ran the multicast test utility that came with the application to validate communication. Part of the utility requires you to specify which IP address to go out on. We tested by specifying localhost, which worked for two of them, but a third wasn't able to communicate with either. This was rectified when I specified on the 3rd box that it should use the static IP associated with the active ethernet port. None of the other 3 ports are connected to anything. How does localhost tie to a particular interface? The network config is the same for all three boxes, except for the ip addresses, the route tables appear to be consistent (although I might not be specifying the right command-line arguments to see the necessary information).