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I own several domains, all hosted with Northhosts, but however I register my domains at GoDaddy (since they're cheaper).

When I receive my 'New Account Information' email from Northosts, they always supply two domains, and GoDaddy always wants me to enter at least two nameservers when changing the nameservers.

I recently renewed an old domain that I have with another provider, and I noticed that they too require/give two nameservers.

What is the reason for this? Why is it not possible to use just a single nameserver?

  • It's not required to have two nameservers. – William Edwards Aug 7 '14 at 8:53
  • @WilliamDavidEdwards Yes it is. Read up on the subject. The question asks WHY we need two nameservers, not 'do we need two nameservers'. – AStopher Aug 7 '14 at 9:01
  • I know, but we don't necessarily need two nameservers. – William Edwards Aug 7 '14 at 10:48
  • @WilliamDavidEdwards The majority of providers force their customers to enter/use two nameservers. Therefore it is concluded that two nameservers are in fact required. – AStopher Aug 7 '14 at 10:59
  • Yes, they do, but they're not required in order to let a domain name function. – William Edwards Aug 7 '14 at 11:56
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+100

From ServerFault:

The requirement to run two nameservers comes from §4.1 of RFC 1034, and is indeed for redundancy.

There are numerous providers who will offer you very cheap "secondary DNS" service where they transfer the zone file from your primary server using AXFR. For example, in the UK we have a well-known provider who'll do secondary service for 50 domains for just £2.30 a month (just over 3 bucks).

This will give you the ability to manage and run the zone yourself, but still give you the resiliency you need.

And another source:

The DNS specifications require that each domain name is served by at least 2 DNS server for redundancy.

Basically, it boils down to redundancy. If one DNS server goes down, the other can pick up the slack. If it didn't exist and your only nameserver went down your site would be down for anyone who could not receive a cached copy of your DNS zone information.

  • on some registrars you can get away with using the same ns twice. or even use cnames to a ns. – Frank Aug 11 '14 at 5:51
  • @Frank Using the same NS twice will be flattened at least at the registry, if not before. As for CNAME they are frowned upon for nameservers. – Patrick Mevzek May 24 '18 at 20:21
  • This requirement does not make a lot of sense without any context. The 2 nameservers could be: on the same machine (different IPs or just 2 VMs/containers on same host), in the same network, in the same datacenter, under the same AS. In all of these cases having these 2 does not provide any kind of fail over: when one is unavailable the other one will probably be too. On the contrary even with one nameserver, if it is fully anycasted, you could have better fault tolerance. Anyway, it is mostly free nowadays, except some registries fixing a minimum, and sometimes doing technical checks. – Patrick Mevzek May 24 '18 at 20:23
  • RFC1034 §4.1: By administrative fiat, we require every zone to be available on at least two servers. ;-) – Patrick Mevzek May 24 '18 at 20:29

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