Conference decwet::winnt-clusters

608.0. "2 NIC cards on one subnet?" by CIVPR1::SIMMONS (Mike Simmons (301) 918-5597) Fri Feb 07 1997 18:30

I have a customer who wants to use 2 public connections between the 2 cluster
servers and have all 4 network cards on the same subnet.  Now, I've always
heard that 2 network cards on the systems should be on separate subnets.  The
concerns that I get are that the 2nd ethernet would not take over if the 1st one
fails.  They will be running NT 4.0 and Clusters v1.1.  I'm not comfortable
with having the 2 network cards in each machine on the same subnet, but I
don't have anything concrete about why this won't work, or potential problems.

I tried failing each of the 4 connections (by disconnecting at the repeater) 
between the machines and used NET TIME \\server as a test of restored NBT 
communication.  Sometimes, it took several minutes, (and 1 or more retries) 
but eventually the command would succeed.  (By the way, this failover would 
also take several minutes when the NIC cards where on different subnets--
However, no routers were involved.)  I did see some strange behavior with FTP 
from one of the cluster servers to a failover IP address with a broken 
connection: login would succeed, but 'ls' would hang.

Is this even supported?  If not, why not?  What are the disadvantages of
having the 2 NIC cards on the same subnet?