Hi all,
I have a basic question.
My two machines are connected back to back and each machine is having two Ethernet Adapters. Failover is enabled. Now when I unplug one of the nic, should failover work ?

Machine A - eth0 - 10.10.10.1 netmask 255.255.255.0
- eth1 - 10.10.11.1 netmask 255.255.255.0

Machine B - eth0 - 10.10.10.2 netmask 255.255.255.0
- eth1 - 10.10.11.2 netmask 255.255.255.0


Now, eth0 of machine A is connected with eth0 of Machine B
and eth1 of machine A is connected with eth1 of Machine B

Now, I am doing ping 10.10.10.1 from machine B. Then I am unplugging eth0 on Machine B. Then should failover work and ping can continue?

Practical result shows it working.
But, my theroy says that eth1 is in different network altogether and it should not work. For failover to work, everything should be in same subnet/network.

what is this "failover" you're talking about? where did you see it??

only way i'd expect that to work is if the client machine is using the peer as the default gateway, so when the 0 metric local route dissapears it'll go via the other machine as a last resort and get lucky.

I am talking about network card failover.
I have got two port network card from my vendor and manual says that port-2 is a friend of port-1...
So, in case, port-1 somehow fails, port-2 will be start working and to make it happen, I have to write some values to /sys/.../*/

a friend??

in case port1 fails, port2 will take his place

well yes i understand what that would mean in layman's terms, but there's no way any technical manual would describe anything as a "friend". I was after a technical explanation of what protocols would be involved in doing this and such. there has to be some sort of mechanism to monitor port status and such, a bit of hardware won't just do it by itself.

so show us the state of the ifconfig output on each machine before and after your simulated failure, and ping and traceroute outputs to match.