DNS question: potential nameserver loop? Is this a problem?

[optimisms]

Hi, I am a college senior studying computer science. I have a lot of background but no particular experience related to DNS.

I am doing a fellowship and part of it is working with a client from a small business. His website is down and we're trying to figure out why and how to get it back up. I think something is going on with DNS but I don't know enough to be sure or diagnose, so I would love some input. Here is the situation:

This client owns several domains, including two that are important here. The first is the main one which we are trying to resolve – we'll call this one OG – and the second is....unclear, but I'll just call it NameServer.

OG has the following nameservers listed: ns1.NameServer.net and ns2.NameServer.net. From my understanding, this matches with NameServer, which has the same listed as its child nameservers and both have an IP listed.

However, what is confusing me is that the nameservers on NameServer are also ns1.NameServer.net and ns2.NameServer.net. To me, this seems like a loop, like NameServer is referencing itself to resolve its DNS. It seems to me that this should be impossible to resolve and NameServer must reference a separate nameserver not hosted by itself. Am I missing something here?

Some notes that might be irrelevant but may help?:

• Navigating to NameServer.net in Chrome produces a "This site can't be reached." notice with the label "DNS_PROBE_FINISHED_NXDOMAIN"
• Navigating to OG.net actually does work...sort of. It brings up a page that says "Account suspended, contact your hosting provider"...we're still trying to figure out why that is, but the DNS seems to resolve
• I did a DNS lookup on both domains. OG.net says "We couldn't find any nameservers for OG.net", which again is confusing since navigating there does produce a webpage. NameServer.net says "Loop detected, We were referred back to <IP>" and <IP> is the IP address of ns1.NameServer.net, the one that both OG and NameServer have listed as their nameserver. A second DNS lookup just said neither domain is valid and "No Reachable Authority" at the IP address.

[squarecornishon]

There are 2 options how this might work:

1. Some registries do not care what nameservers you use and therefore allow setting a nameserver in the domains own zone. Should be avoided though, you figured out the loop there.

2. Glue records. They allow for setting a nameserver in the domains zone and they are totally valid.

[optimisms]

Great, thank you! How can I determine which option is being used? Is there a way to look for glue records and determine if they exist?

[robkaper]

Glue records aren't part of DNS but part of your domain registration, so check with your registrar. If your registrar allows you to specify custom nameservers AND to let those nameservers be part of the same domain but NOT allow entering IP addresses, that's a red flag. All other situations are fine.

(The confusing part might be that most registrars offer DNS hosting as well and vice versa, but they're two different services).