Q. I've just install CentOS version 5.x and my system keeps losing the default gateway on reboots and network restarts.

A. It seems like a bug and has been reported on trixbox as well. A quick way to fix it is to run system-config-network and configure all the parameters. Even if you have the proper settings, make sure you hit the Save button. The gateway should stay there after reboot/network restart.

If that doesn't work, add something like this in you /etc/rc.local script:

route add default gw 192.168.1.1

Replace 192.168.1.1 with whatever your gateway is.

Careful when you do this - make sure you remember this change next time you need to change the gateway, otherwise you'll be pulling your hair.