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The domain rspb.org.uk has the nameservers

ns1.namecity.com. ['62.128.193.35'] (NO GLUE) [TTL=172800]

ns2.namecity.com. ['84.22.161.171'] (NO GLUE) [TTL=172800]

And on the website intoDNS, there is this warning:

The parent nameserver ns1.nic.uk is not sending out GLUE for every nameservers listed, meaning he is sending out your nameservers host names without sending the A records of those nameservers. It's ok but you have to know that this will require an extra A lookup that can delay a little the connections to your site.

In the registrar's settings, I can change these nameservers, but it only allows names, not ip addresses.

My question is, how does the DNS server know the ip address of the nameservers?

I did read somewhere that all nameservers must first be registered in the registry so perhaps an IP address is required during this step. The intoDNS warning mentions "an extra A lookup". Where is the DNS looking?

Lars
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2 Answers2

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An "A lookup" is the standard DNS query that happens when a client needs to know the IP address for a given hostname like www.example.com.

In this context, it means you get the info that ns1.provider.com is the relevant DNS server for www.example.com and without glue records an extra A query for ns1.provider.com is necessary. This works exactly like all other queries. In the end, you get an IP address for ns1.provider.com and can contact it to get the info you want.

In many cases, like the constellation I outlined below, glue records are not strictly necessary, but it's easy to construct circular dependencies that require glue to break the circle. An example: If you specify ns1.example.com as a nameserver for example.com, you must provide glue for this to work, as ns1.example.com could never resolve otherwise.

Sven
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Glue is only really needed if the nameservers for a domain are in that same domain, so technically you are fine since yours are in a different domain. As the message says It is just a bit slower, but unless you are Google you do not need to worry about this ;)

How does the DNS server know the ip address of the nameservers? It looks them up in the namecity.com domain. The problem would only arise if the nameservers are in the same domain, thats why you need a glue, to avoid chicken and egg situation.

If you care about this, glue records are usually not called glue in the registrar web interfaces. In mine there is a separate menu entry called "register nameserver", so try clicking around on anything that has nameserver in it ;)

Aleksandar Ivanisevic
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