Reverse DNS

[Steve]

Name: cohqmg02.uk.ngrid.com
Address: 194.128.150.248

nslookup 194.128.150.248

*** localhost can't find 194.128.150.248: Server failed

;; res_mkquery(0, 248.150.128.194.in-addr.arpa, 1, 12)
------------
SendRequest(), len 46
HEADER:
opcode = QUERY, id = 45038, rcode = NOERROR
header flags: query, want recursion
questions = 1, answers = 0, authority records = 0, additional = 0

QUESTIONS:
248.150.128.194.in-addr.arpa, type = PTR, class = IN

------------
------------
Got answer (46 bytes):
HEADER:
opcode = QUERY, id = 45038, rcode = SERVFAIL
header flags: response, want recursion, recursion avail.
questions = 1, answers = 0, authority records = 0, additional = 0

QUESTIONS:
248.150.128.194.in-addr.arpa, type = PTR, class = IN

------------
*** localhost can't find 194.128.150.248: Server failed

Can anyone explain why I can't do a reverse lookup up on this IP ?
/me is confused :0(

[Jim Reid]

>>>>> "Steve" == Steve <g_a...@hotmail.com> writes:

Steve> Can anyone explain why I can't do a reverse lookup up on
Steve> this IP ? (194.128.150.248)

The reverse zone for this address (150.128.194.in-addr.arpa) is
delegated to ns0-01.dns.pipex.net and ns1-01.dns.pipex.net. Neither of
those servers knows about this zone. To make matters worse, they both
accept recursive queries. So when someone does a reverse lookup of
194.128.150.248, their name server ends up querying one of those two
servers which then try to resolve the queries. When those servers find
that the delegation for 150.128.194.in-addr.arpa points back to
themselves, the lookups fail with the SERVFAIL error.

I have Cc'ed the addresses in whois and the SOA record for pipex.net,
so hopefully this reply will be seen by someone at pipex.net who can
fix the problem. If not, complain to them.

BTW, you will find that dig is a far better lookup tool than nslookup.