Default routing setup

[Sunny Shum]

Hi all,
 
I am a newbie into the Linux world, and I recently built a firewall box (2
NICs, internal network as 192.168.1.xxx) with RedHat 9.  Everything works
fine, except the routing table.  Every time when the system has reboot, I
have to do the following command:
 
prompt>route del default
 
prompt>route add default gateway xxx.xxx.xxx.xxx [external gateway IP]
 
Because I don't do that, and if I just type "route" at the prompt, the
default is point back to the internal NIC.  Is there a way to make this
permanent?  I tried to edit the file /etc/sysconfig/network by adding the
line "GATEWAY=xxx.xxx.xxx.xxx" but it doesn't work.
 
Thanks!
 
Sunny Shum