Some websites not working after AT&T circuit switch
 

First, my qualifications. I'm a trained Microsoft and Cisco guy who inherited a network with Linux servers and I'm working on training myself to use Linux.

Story (short version) - AT&T was raking this company over the coals for a T-1 line. In order to change the contract, AT&T setup a new circuit and sent out a new router configured to use the same IP addresses as before. Every since the change over, users are not able to get to every website they have used before, some emails are not going out and some vendors are not able to get email to us.

What I've done - I called AT&T to have them check the configuration of the new router to make sure it is allowing all traffic through. When I was not able to get a tracert to www . spectrumwatch . com (take spaces out of site address) to get past my internal default gateway, AT&T backed off and said it wasn't their problem. I have a Linux box (Red Hat 9) set up as the router to the internal network. A former employee (who really doesn't have the time to help me) suggested there may be a problem with the iptables. I figured out how to open the iptables and iptables-config files but I have no idea what I'm looking for.

Can someone tell me if I'm on the right track, what to look for in the iptables, or where I should be looking to troubleshoot the problem.

Your help is greatly appreciated.

More Info
 

I was able to connect directly to the AT&T router and get full access to the websites in question. That leads me to believe it's a server problem.

Thanks again in advance.