We have multiple sites in IIS with different IP addresses. This is cool, want different IPs to all go to this server and use the proper site. However I discovered an issue that when the server makes an outgoing connection, I cannot predict which IP it will use. I had to have one client add ALL the IPs to their firewall so that a certain service could communicate with their server. Well now the time has come to add another IP/site to IIS but I had told them they would not need to add any more IPs. So the question is, how can I make Windows Server 2003 use only ONE specific IP for outgoing calls instead of it being unpredictable?

If this is not a good enough description, when I was RDPed into the server and I opened IE and went to 'what is my IP' it was sometimes different which is how I discovered why the one client's firewall was suddenly refusing the connections.

How can I just make outgoing calls originate from a static IP yet still allow multiple IPs pointing to different sites in IIS?