I have added a second ethernet to a host in order to route backups traffic over a second wire (to avoid saturating the main link). I have to rely on network admins on the other side of planet for this, and they gave me a second IP in the same subnet as the main interface.
I attempted to add a route like this to force traffic via the backups link (e1000g1) rather than the main link (e1000g0):
route add 10.0.1.19 192.168.2.1 -ifp e1000g1
10.0.1.19 is my backup server
192.168.2.1 is the gateway for the local subnet
This did not work. If I try to ping the backup server from the host, snooping on both interfaces shows that packets never even go out. I just get ICMP unreachable.
On the suggestion of a coworker, I also tried this variation:
route add 10.0.1.19 192.168.2.5 -ifp e1000g1
Where 192.168.2.5 is the interface address for e1000g1. That has the same result.
Is it possible to make this work, or do I need to have two separate subnets for this to work?