I was onsite earlier this week helping out a friend with his SBS 2003 installation. He had done the install himself and all things looked pretty much ok. He had applied W2003 Service Pack 2 as well. I showed him how to setup computers and all worked well – he added the computers to the domain and proceeded to use the server for a week or so without problems. His server is a 2 NIC installation and he was running SBS 2003 R2 standard ie – without ISA 2004. I visited site to help do the ISA install and make sure things worked fine. ISA went in just fine and we could then surf the web without problems. One interesting thing though was that SBS Companyweb would not display. It worked fine before installing ISA on the server but would not work at all on the workstations. The natural thing to point the finger at was therefore ISA – I mean it was the only thing that had changed recently.
Accessing http://companyweb came back with a DNS error. I attempted to do some diagnosis of this problem and found I could ping the server by name just fine, but companyweb would not resolve to an IP at all. I checked DNS to confirm that it had the normal CNAME record for companyweb pointing to the SBS servers name and it was there just as it’s supposed to be. Ok – so I wondered why won’t this resolve?
I thought I would try another approach. I added an A record called WRSTEST and pointed it to the SBS severs IP – this worked fine and I could ping the WRSTEST without issues. I then created WRSTEST1 as a CNAME record and tried to ping again. It didn’t work – it would not resolve the CNAME record, but it would resolve an A record. Something real strange here I thought and then it hit me… Strange things on a W2003 server with Service Pack 2 on it are ALMOST ALWAYS caused by RSS/TCPA/TCPChimney being turned on.
I had not checked this on his server as it was something that I do by default these days when I install a server and didn’t think to check it earlier given that it was working fine. So I ran the reg hacks to disable these bits on the TCPIP stack, rebooted and things worked just fine again.
So – I fixed the problem, and in the course of investigating it realised that this issue can affect much more than simple communications.