Zombie Web - The Old Site That Won't Die

Posted: 24/06/10

Down & Dirty With DNS

I got sucked into a rather weird problem this week. I was asked to investigate the ghost of an old web site that kept reappearing at random. I should point out that this site was nothing to do with me - I was simply asked if I might know what was going on since the persons concerned were becoming rather exasperated.

The site had moved to a new hosting provider a week or so back and had been totally revamped, and thus it was a bit annoying for the client to see the old site popping up like a zombie intermittently. A period of more than a week tended to rule out any sort of DNS caching or propagation issues, so something was definitely broken.

After a bit of probing, I discovered that the whois record for the domain had been updated with the new DNS servers. All well and good, but whoever had set up those new servers had botched the job. They'd added the new A/CNAME records but left the "NS" records pointing to the old name servers, rather than the new ones.

The effect here was rather interesting, since asking the new name servers where "www" was resulted in the new addresses, asking them for the ns records resulted in a referral to the old nameservers and subsequently the old www addresses. Depending on your DNS resolvers, you got the old or the new.

Applying a little "pressure" to the new hosting company cleared the problem up.