OK, forget my brief lapse of stupidity earlier. : I just needed someone to remind me I already knew how to do this. :P
ifconfig eth0:0 192.168.10.1 netmask 255.255.255.0 up
route add -net 192.168.10.0 netmask 255.255.255.0 eth0:0
If you want it permanent, just copy your current /etc/sysconfig/network-scripts/ifcfg-eth0 to /etc/sysconfig/network-scripts/ifcfg-eth0:0 and edit the setting as required.