We're switching internet providers, so when the new router was connected, I needed to switch my ISA 2000 server to it, changing only the external address, and voila, everyone would now be surfing on the new T1. But no luck at all. To troubleshoot, I plugged my laptop directly into the new router and through DHCP, got my IP info and was able to surf no problem. So I connected the ISA server's external NIC and set IP config to use DHCP, and saw it assigned the IP, Subnet, gateway, and DNS settings, same as the laptop (except the IP was 1 higher, as expected). I don't assign any settings in ISA by IP address - I think the only place is for IP filtering anyway ('default external IP address' assignment). The connection is fine outside of the browser, because I can both Ping and Tracert to destinations without problems, and DNS is resolving. I initially didn't have the external addresses in the LAT, which I believe I should not have to (LOCAL being the operative word here), but have tried it either way. Using a browser from that server or any other machine on the network will usually result in a 502 error, or tries to load the page, then just stop (nothing displayed, no error message). I've restarted both the server and any workstation, as well as stopping/restarting the proxy services when I didn't restart the server.
The very second that I enter the old IP address into IP settings (no DHCP with the old router) and plug the old cable in, I can browse with the server and any other machine on the network. I thought I had a 2 minute job, but I'm absolutely stuck here....Where else do I need to make an IP address change, or am I missing something completely different?