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I have two glue records at Godaddy, for example:

NS1.MYDNSSERVER.COM
NS2.MYDNSSERVER.COM

And I have three NS records in my domain:

NS1.MYDNSSERVER.COM
NS2.MYDNSSERVER.COM
NS3.MYDNSSERVER.COM
  1. If I have glue records why do I need the NS records?
  2. The extra record (NS3.MYDNSSERVER.COM) is a real DNS server but from some reason I can't update this record as a glue record. Can this cause any problems?
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If I have glue records why do I need the NS records? - because that is the way the protocol was designed. You need NS records to delegate the zone, you need glue records if you are delegating the zone to servers with host names, that are within the zone you are delegating to. –  Zoredache Dec 11 '12 at 20:08

1 Answer 1

Glue records are "hint" IP addresses that the parent servers (i.e not GoDaddy) provide in addition to the answer when a resolver asks what the NS records are for your domain. They are not the authoritative answer. The records you have labeled above as glue records are not glue records, however GoDaddy probably use those records to tell the parent nameserver what the glue should be. The canonical DNS answer describes this much better than I am able to.

Some resolvers will use the glue records without double-checking and some will query the NS records from the authoritative name servers (the ones provided in the glue records) to make sure they are actually correct.

I know from experience that PowerDNS is in the former group and bind9 is in the latter. I have no experience with any other resolvers.

Not having NS records at your nameservers will cause problems with bind9. The kind of problems where anyone whose ISP is using bind9 will not be able to visit your website.

Having an extra NS record at your nameservers that isn't at the parent nameservers will just mean that nameserver gets less traffic than the other two. It's the other way around in this situation and bind9 will use all the nameservers and PowerDNS will not.

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tnx, And what about the NS3 record I have in the zone file and I don't have in the glue record? –  Noamway Dec 11 '12 at 20:45
    
Once a sever has reached you DNS servers, it can and three NS servers for additional queries. However, it can only use one of the two listed with GoDaddy to find your DNS servers. –  BillThor Dec 12 '12 at 0:35
    
NS3 thinks it is authoritative for the domain, and NS1 and NS2 may think it is authoritative for the domain, but no other name server does or will when querying for your name servers. If you want NS3 to be seen as authoritative for your domain then it needs to be listed with the parent server as a name server for your domain. You need to add NS3 to the list of name servers for your domain at GoDaddy. –  joeqwerty Dec 12 '12 at 0:38
    
tnx, but if I will not add it to Godaddy does it can make me any problems, does it correct according to DNS rules? I remind that the NS3 is still function DNS server but not set in Godaddy. –  Noamway Dec 12 '12 at 5:15

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