Reverse Namelookup for a classless subnet

[Kevin Darcy]

Sumit Mehrotra wrote:

> Hi Users
>
> Here is the INFORMATION first about my setup ( QUESTIONS follow)
>
> I have 2 IP addresses at present, with name servers provided by my ISP. Now, I am trying to make a NS ( running in a different domain altogether, from the 2 IP addresses), the Primary NS for a webservers running on these 2 IPs.
>
> I have set up the configuration files and dealt with the firewall issues.
>
> At present I can do a nslookup/dig for the name of the webservers from inside and outside the domain that the NS resides in ( behind firewalls).
>
> For the reverse lookup, from inside the NS domain I get the following answer :
> DIG
> ---
> ; <<>> DiG 8.2 <<>> @dhruv.bu.edu 20.10.197.128.in-addr.arpa ptr
> ; (1 server found)
> ;; res options: init recurs defnam dnsrch
> ;; got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
> ;; QUERY SECTION:
> ;;      20.10.197.128.in-addr.arpa, type = PTR, class = IN
>
> ;; ANSWER SECTION:
> 20.10.197.128.in-addr.arpa.  1D IN PTR  pharos.bu.edu.
>
> ;; Total query time: 0 msec
> ;; FROM: dhruv.bu.edu to SERVER: dhruv.bu.edu  128.197.14.80
> ;; WHEN: Tue Nov 14 20:41:14 2000
> ;; MSG SIZE  sent: 44  rcvd: 71
>
> Notice that the Authority Bit is not set, when it should have been set.
>
> For Outside the NS domain, I get the same answer.
>
> Additionally, the reverse nslookup for the address fails unless I add an in-addr.arpa to it. (This baffles me!)
>
> QUESTIONS :
>
> Is it something to do with delegation of the in-addr.arpa space by the ISP to my new NS?

Is dhruv.bu.edu supposed to be authoritative for 20.10.197.128.in-addr.arpa? It appears to have an SOA and PTR for that name, but no NS records, and, as you noticed, it's not answering authoritatively for the zone. You can't load
a zone that has no NS records. This should have been obvious from the error messages in the logs.

> If so will it be done automatically, if I go and change the NS for it, on the Web based form that they have?

Who? What? Do you really expect us to know your ISP's internal procedures?

By the way, dig's "-x" option is your friend.

                                                                                                                                                    - Kevin