To view the routing table, use the:
route -n
Adding a default gateway manually:
route add default gw <IP_adresa>
Delete the default gateway manually:
route del default gw <IP_adresa>
These changes are temporary. To permanently set the default gateway in the file /etc/sysconfig/network
GATEWAY=<IP_adresa>
For multiple interfaces on the same subnet, you can set a preferred route:
GATEWAYDEV=<rozhraní>