Routing traffic internally on Rackpsace

DO NOT SET YOUR APPLICATION UP TO USE EXTERNAL IPs. We ended up with a huge bill that month since it turns out we were routing all our traffic outside of Rackspace's cloud and then back in, which significantly upped our outgoing bandwidth which rackspace is now currently charging at 18cents/GB. In a high traffic environment this can add up to some high numbers which are not good for your bank account.

After spending some time talking to Rackspace Support, the solution, as you can probably tell, was to route traffic inside the Rackspace cloud and behind their subnet mask. So to find the IPs to use ssh into each server and run...

ifconfig eth1

...and that's it. This will spit you back what Rackspace uses internal and thusly what you won't be charged for. Eth0 will be your external IP. Change this in all the appropriate locations.

Note: if you're running VPNs/firewalls be sure to change your iptables as well