Best of the ISP-Lists

Name Server Rules

Members of the ISP-Webhosting list find that there are a wide variety of myths, understandings, and assumed procedures when setting up name servers.

[February 3, 2003]

On the ISP-Webhosting list in January, IP asked:

I checked out a domain today on the whois list. I noticed that this domain holder had registered two name servers but they both have the same ip. How does one do this? I was under the impression it was not allowed. I suppose for a small office on a T-1 that is OK but not for a hosting business.

[DS said] "It works, but it's not recommended—certainly not recommended in the relevant RFC (I've forgotten which one that is)."

[JK explained] "It really does not matter. You could have one, two, three, or none.

• As a rule of thumb it is good practice to have more than one (for redundancy)
• Also, have them on different servers (for redundancy)
• Also, have them on a different subnet (for redundancy)
• Also, have them on a different network (for redundancy)
• Also, have them at two different physical locations (for redundancy)

But not everyone does that. Microsoft recently learned what happens when all your DNS servers are in the same physical location, and or on the same network.

However, again, it does not really matter in a whois list. There is no law that says you have to list two as a minimum and that they have to be on different boxes or IP addresses or whatever.

Competitors of ours used to tell our customers that either had no DNS listed or did not have their domain pointed at a website that they would have to forfeit and return their domain name as they were in violation of domain name rules. What a strange world!"

[JJ added] "There are some registrars that don't allow duplicate IPs for name server registrations (Network Solutions is a prime example), but some do. In any case, you should have diversity on your DNS servers. They should be at different locations and on different networks as broad as possible.

Don't assume that having a single public IP address means that there is a single server. I personally load balance a single outside DNS IP address to 6 dedicated servers located at 3 different geographically located data centers."

—End