Linux: add static route permanently

# cat /etc/redhat-release
CentOS release 5.4 (Final)

- config ( /etc/sysconfig/network-scripts/route-eth# )

# cat /etc/sysconfig/network-scripts/route-eth0
192.168.10.0/24 via 192.168.20.1
20.0.0.0/24 via 192.168.20.1

- after rebooting OS

# netstat -rn | grep eth0
192.168.20.0    0.0.0.0         255.255.255.0   U         0 0          0 eth0
20.0.0.0        192.168.20.1    255.255.255.0   UG        0 0          0 eth0
192.168.10.0    192.168.20.1    255.255.255.0   UG        0 0          0 eth0