On reboot network settings are defined by initialization scripts. If changes you tried are good, you have to edit system's network configuration files. Either run (in the graphical environment from root) system-config-network or edit /etc/sysconfig/network and change the gateway or any other parameter you need.
In the latter case you need also to manually restart the network (/sbin/service network restart) to make changes effective.
Last edited by hopbyhop; 11-10-2008 at 11:47 AM.