I have RED HAT Linux version 3 (RHEL) and file
/etc/sysconfig/network-scripts/route-eth0 use to configure static routes:
less /etc/sysconfig/network-scripts/route-eth0
Code:
GATEWAY0=10.10.1.1
NETMASK0=255.0.0.0
ADDRESS0=10.0.0.1
GATEWAY1=10.20.1.1
NETMASK1=255.255.0.0
ADDRESS1=192.168.1.0