Have you ever had your Web site just drop off the face of the 'Net even though you know that the server was running? One of the most common causes of this problem is a misconfigured or damaged DNS set up and if you've ever tried to get seriously under the hood with DNS you'll know just how complicated this can be.

Given how crucial DNS is to keeping your presence visible on the Internet there’s an obvious need for sophisticated diagnostic services and that’s the niche that DNSstuff.com fills.

DNSstuff has taken pretty much every DNS tool and diagnostic in existence, re-written them, and integrated the results into a hosted Web application. The company explained to me that the rewriting of the standard tools was done so they could extract more information from the interrogation and response processes giving them deeper diagnostic insight.

What prompted me to take a look at DNSstuff was a letter from a Network World reader, Art Grater (Pebble Beach, Calif.) who was interested in what the company had to offer. He used DNSstuff’s ‘check out your own site’ feature and was amused to find when he entered dnsstuff.com as the target the domain was reported to have two critical errors!

Unfortunately before you get an account (you can register for a free 21 day trial), you can’t see the details. The ironic aspect of this meant that I just had to find out what was going on …

I had a discussion with DNSstuff’s CTO, Paul Parisi, and he explained that one of the two errors is caused by their diagnostic server being on the same network as their mail server and therefore the mail server is being seen as an open relay from inside their network. He pointed out that obviously this isn’t the case from the outside.

The other error is apparently in their use of CNAMEs to identify their servers so that the F5 load balancing they use can work. Paul told me that the reason this is shown as an error is that while it doesn’t cause a problem, this technique isn’t defined in the relevant RFCs and therefore by omission is a potential problem. Paul also told me that they checked the technical issues with one of their advisers (a god of DNS), Criket Liu, who told them that what they are doing is OK despite its dubious status. This rather underlines just how complex DNS actually is!

is a consultant, author, journalist, columnist and blogger.

SQL error at node_info: Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)