There's another way to do this (at least it has worked for me in the past).
The IP used for outgoing connections is normally the first IP allocated (e.g. that of eth0 as opposed to eth0:1/2/3/4/5/6 or whatever).
So a quick edit of your /etc/sysconfig/network-scripts/ifcfg-eth0 and so on, swapping the IP in that with whichever other file has the one you want to go out on should do the trick. You'll need to do a "service network restart" afterwards.
Please be very careful though. It is easy to screw things up and this may not work on your distro anyway. So don't blame me if it all goes horribly wrong :-(
Faris.