I've just performed a new installation of the very latest (Fall, 2008) version of Fedora 9 Linux and am perplexed that it never set the default route properly and that even traveling the labyrinthine ways of this OS, there's no obvious way.
Of course, it's clear that one can do it on a one-off basis like this:
route add default gw gw1 metric 0 eth0
ip route add to default via 192.168.2.1 protocol static
The gateway is normally set in /etc/sysconfig/network-scripts/ifcfg-eth0, not in /etc/sysconfig/network. For example, on my current machine:
NETWORKING=yes NETWORKING_IPV6=no HOSTNAME=flyboys NISDOMAIN=ekcineon
DEVICE=eth0 ONBOOT=yes HWADDR=00:1d:09:31:3a:cc NETMASK=255.255.255.0 IPADDR=22.214.171.124 GATEWAY=126.96.36.199 TYPE=Ethernet
Note that I set HWADDR because I have two ethernet cards and I want to make sure the right one is assigned to eth0. The configuration for the second card is in /etc/sysconfig/network-scripts/ifcfg-eth1