rehhat arp problem with two interfaces

Hello friends.
I have a problem with my redhat server and need your help.my server
have two NIC. eth0 : 150.0.0.70 , eth1 : 128.212.250.84 . when one
host want to contact with eth0 via a router, the server returns eth1 mac address and host cannot ping 150.0.0.70.when I wrote an arp command in my router problem solved.I want to know what’s wrong with my server.
thanks for your guides