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DNS Delegation Check: Test the Name Servers of a Domain

This free DNS delegation check starts at the root servers and follows the path down to your domain. It compares the name servers the registry lists with the ones in your zone, and finds lame delegation and missing glue.

By Debmedia Technologies LLP · Kolkata, India · Updated

What Is a DNS Delegation Check?

A DNS delegation check tests whether the name servers that the registry lists for your domain are the right ones, and that they answer correctly. When you register a domain, the registry stores a list of name servers for it. That list is called the delegation. If it is wrong or out of date, visitors may not reach your site, even though your zone itself is perfect.

This DNS delegation check starts at the root servers and follows the path down, the way a resolver does. It then asks every delegated server directly and compares what it hears with what the registry says.

How to Use This DNS Delegation Check

  1. Enter your domain, for example example.com.
  2. Press Check delegation. The walk down from the root can take a few seconds.
  3. Read the checks at the top, then the delegation as the parent sees it.
  4. Review what each server says, and the path that was followed.

What the Test Looks At

CheckWhy it matters
Number of name serversAt least two are needed so one failure does not take the domain down.
Network diversityServers on different networks survive a single network failure.
Glue recordsA server inside your own domain needs an address stored at the registry.
Lame serversEvery delegated server must answer as an authority for the domain.
Parent and zone matchThe list at the registry should equal the NS records in your zone.
SOA serialServers with different serials may hold different versions of the zone.
DS recordShows whether DNSSEC is switched on at the registry.

The delegation model comes from RFC 1034, which describes how delegation works, and the advice on server placement from RFC 2182 on running secondary name servers.

Common Delegation Problems

The registry still lists the old name servers

After a move to a new DNS host, many owners update the zone but forget the registrar. The check then shows a difference between the parent list and the zone list. Update the name servers at your registrar.

A lame delegation

The registry points to a server that does not know your domain. Add the zone at that provider, or remove the server from the delegation.

Missing glue

If your name servers are named inside your own domain, such as ns1.example.com, the registry must store their addresses. Add a glue or host record at the registrar.

A server that does not answer

It may be down, blocked by a firewall or missing an address. Fix or replace it.

For a wider health report on the same domain, use the DNS health checker. To list the name servers, try the NS lookup, and for the DNSSEC side, use the DS record lookup. After fixing the delegation, watch the change spread with the propagation checker.

Frequently Asked Questions

It is how a parent zone, such as com, tells the world which name servers answer for a child, such as example.com. The list is stored at the registry and set at your registrar.
A delegation is lame when the parent points to a server that does not answer as an authority for the domain. Lookups that reach it fail or slow down.
Glue is an address stored at the parent for a name server that lives inside the domain it serves. Without it, resolvers cannot find the server, because they would need the domain first.
They are changed in two places: at the registrar for the parent and in the DNS zone for the child. After a provider change one is often forgotten, and the check shows exactly which.

Disclaimer: results come from live requests and can change as records and servers change. We cannot guarantee that every answer matches what every visitor sees.