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I used Robtex.com for an online DNS analysis, I'm confused about the meaning of "the name of name server"

for the domain name "some_domain.com"

robtex returns "The names of name servers are" :

ns1.maroc-telecom.com *
ns2.maroc-telecom.com *
ns3.maroc-telecom.com *
ns4.maroc-telecom.com *
ns1 maroctelecom.com *
ns2.maroctelecom.com *
ns4.maroctelecom.com *
dns.menara.ma *
dns1.menara.ma *
dns2.menara.ma *
dns3.menara.ma *
adsl-227-108-192-81.adsl.iam.net.ma *
adsl-228-108-192-81.adsl.iam.net.ma *

I understand that name servers are NS records for some_domaine.com, PTR records are the domains corresponding to ip adresses of NS records, but I coulnd't understand what "names of name servers" are ?

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  • 1
    I've fixed up the formatting of your question, but honestly, you will get better help with this if you disclose the domain name in question, so we can look at the records ourselves.
    – MadHatter
    Jul 3, 2014 at 12:29
  • Having looked a bit closer at this, the question appears to have more to do with robtex.com (misspelled in the question) than with dns in general. Jul 3, 2014 at 12:46
  • MadHatter thank's | @HåkanLindqvist sorry, I can't disclos it
    – aboujanane
    Jul 3, 2014 at 12:59

2 Answers 2

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When you specify name servers in DNS they are defined by name. These first few names are typically names for name servers, so I believe these records are the names listed in the NS records for the domain. I am concerned with the number of name servers, as normally there are 2 to 8 name servers for a domain. It appears the presented list of names also includes the names returned by looking up the addresses of the NS servers.

The IP addresses listed should be the IP addresses obtained from the A record for the names servers.

It is common for an IP address to have multiple associated names. PTR records are usually configured with only one name. Many ISPs by default configure their PTR records to indicate the service type, and some additional information. The names beginning adsl appear to be of this form. With the exception of servers sending email to the Internet, there is no requirement to have names on PTR records to match an A record which points to them.

Try doing the lookups for yourself. You can use host or nslookup to find the IP address and corresponding PTR names.

bill@localhost:~$ host ns1.maroc-telecom.com
ns1.maroc-telecom.com is an alias for dns.menara.ma.
dns.menara.ma has address 81.192.108.227
bill@localhost:~$ host 81.192.108.227
227.108.192.81.in-addr.arpa domain name pointer dns.menara.ma.
227.108.192.81.in-addr.arpa domain name pointer adsl-227-108-192-81.adsl.iam.net.ma.

You can use these commands to look up the name servers for the domain.

bill@localhost:~$ host -t NS example.com
example.com name server a.iana-servers.net.
example.com name server b.iana-servers.net.
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  • "When you specify name servers in DNS they are defined by name"; true, except when the name servers are inside the domain in question, which is why I wish the OP had not redacted the original domain name.
    – MadHatter
    Jul 3, 2014 at 12:31
  • @MadHatter The resolver will contain IP addresses of the local name servers which may or may not be published as nameservers for the local domain. In NS records they are always specified by name, although they may be specified by a short name such as NS1 if they belong to the domain.
    – BillThor
    Jul 3, 2014 at 12:37
  • True. In glue records, however, things are not so simple. I don't know if the OP is talking about glue records, because I can't check the actual data because he's redacted the domain (and I'm not completely confident that I understand his question). +1 from me anyway, though - your answer seems excellent to me, notwithstanding shortcomings in the question.
    – MadHatter
    Jul 3, 2014 at 12:48
  • @MadHatter Having looked at the output from robtex.com (eg robtex.com/en/advisory/dns/google.com) I'm pretty sure they just wonder what on earth is listed under the "Names of the nameservers of x" headline (as opposed to what is listed under "Name servers of x"). Jul 3, 2014 at 12:52
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While they do not appear to provide any documentation as to what is what, my conclusion after observing the results at robtex.com is that:

"Name servers of example.com" lists the names from the NS records. (Unclear what they show if the delegatory and authoritative records do not match.)

"IP numbers of nameservers of example.com" lists the IP addresses that the names from the NS records resolve to.

"Names of the nameservers of example.com" is not as obvious. It appears to be any names that robtex.com have observed that resolve(d) to one of the IP addresses of the nameservers. (Important to note that this may have nothing at all to do with anything!)

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