How to control on which interface linux replys incoming connections?

I mean : i have machine with two interfaces, say eth0 and eth1, called eth0 and eth1, default route is on eth0. when I ping eth0 from machine on eth0's side of network, it replies, when I ping eth1 from .. on eth0's it replies, when I ping eth0 from machine on eth1's side, it replies, but w

How to control on which interface linux replys incoming connections?

I mean : i have machine with two interfaces, say eth0 and eth1, called eth0 and eth1, default route is on eth0. when I ping eth0 from machine on eth0's side of network, it replies, when I ping eth1 from .. on eth0's it replies, when I ping eth0 from machine on eth1's side, it replies, but