I had the dubious honor the last couple days of breaking up an argument between a Linksys PAP2T and a Linksys WRT54G. You might think they would work well together, coming from the same family and all. Well not really.

The problem was caused by the WRT54G (version 5, btw) which refused to route SIP traffic back to the PAP2T. It was allowing HTTP and DNS traffic just fine, but it balked at SIP for some reason. The symptoms were that the PAP2T kept sending REGISTER requests without a WWW-Authenticate header. For a long time I thought it was a setting on the PAP2T, but instead it was because the PAP2T never got the WWW-Authenticate challenge, so it obviously couldn't respond. A dead giveaway should have been that the PAP2T would send 5 REGISTER requests in a row. It must have figured there was network congestion or something, so it was retransmitting.

The solution was to upgrade the WRT54G from version 1.00.0 to 1.02.2. Some bug in the 1.00.0 firmware caused the issue and now it's resolved. I haven't looked at the release notes to see what it was, and frankly I probably won't. I've never really liked the version 5 WRT54Gs and this just helps solidify it.