Two interfaces on the same network

[AL Chane]

Hi, there:

     I have two interfaces on my linux PC in the same network:

>ifconfig eth0 172.20.1.30 netmask 255.255.255.0
>ifconfig eth1 172.20.1.31 netmask 255.255.255.0

     Another Windows PC with IP 172.20.1.32 netmask 255.255.255.0

     I found that in the same network, Linux PC only use one interface
eth0 for outbound/inbound traffics no matter what. Even if I use Windows
PC (172.20.1.32) to ping Linux PC's eth1 (172.20.1.31), Linux still use
eth0 to reply. That is, if I unplug eth0's wire, eth1 won't work too.

     Does anyone have the same issue on how to make two interfaces
work in the same network? I search 2003 archive, some said it can be
done by set second interface (eth1) netmask to 255.255.255.255, but
i tried and it doesn't work for me.

     Helps from you are highly appreciated!

Thanks

AL