On my Linux platform (Centos 6.3 x64), we have 2 ethernet ports eth0 and eth1. These are configured as follows:
If I connect a cable to eth0 (eth1 disconnected), from within the unit I can ping the router (10.0.0.10) but from my laptop (IP:10.0.0.3 netmask 255.255255.0) connected to the same network I can ping the embedded unit on either 10.0.0.1 or 10.0.0.2 !! This cause a little problem when I want to install virtual machine that will be use only eth1.
I try to install other Linux (debian 6.0.5, fedora 17 distribution but that don't resolve the problem.
Sorry for my English
The behavior your are observing is actually correct for the configuration under default Linux parameters. www.excentral.org/.../two-nics-one-subnet-linux-headaches provides a clear explanation of the cause of the issue and a possible workaround that may apply directly to your scenario. Further detailed discussion is present at serverfault.com/.../2-nics-2-ips-same-subnet. Does that seem to help out?