configuring two network interfaces, same subnet

[Alfredo Aguirre]

Hello people!,

I'm trying to configure 2 network interfaces in the same subnet, because i
want to  use one interface for NS and the other for MX,

if i try
bash-2.05b# ifconfig em0 aa.bb.dd.1 netmask 255.255.255.0
bash-2.05b# ifconfig em1 aa.cc.ee.2 netmask 255.255.255.0
ifconfig: ioctl (SIOCAIFADDR): File exists

ok they both cannot be in the same subnet.

i know that i cannot have them both in the same subnet without modifying
the routing, but im confussed about it.

i also tried after settin' one of the ips, deleting the routing

bash-2.05b# route delete aa.bb.cc.0

and then setting the ip

bash-2.05b# ifconfig em0 aa.bb.dd.1 netmask 255.255.255.

ok i can now set the 2 ips in the same subnet but my DNS stops working,

i dont want to change the submask, for any of my ips

well im confused about it, so i hope you guys could adress me in the right
direction,

Thanks in advance,

Alfredo