[Dnsmasq-discuss] Enabling Reverse Lookup In A Live Environment

Michael Rack dnsmasq.list at michaelrack.de
Sun Nov 16 11:36:47 GMT 2008

Hi Richard,

your ISP have to setup up the correct Reverse-DNS for you!
AT&T 's Nameservers for reverse deligation lookups:


Source: http://ws.arin.net/whois/?queryinput=%2B+

It is AT&T's job to do so, not yours!


Jason schrieb:
> Richard,
>     My connection is a T1 with a /30,  just my IP and the AT&T router 
> on the other end in my subnet...
> I will try to dig up the reverse lookup servers Monday night, but I'm 
> pretty sure it'll be some AT&T server...
> Thank you,
> Jason
> richardvoigt at gmail.com wrote:
>> On Sat, Nov 15, 2008 at 3:59 PM, Paul Chambers<bod at bod.org>  wrote:
>>> Hmm... that's not how I understood it to work (not that I'm a DNS expert...)
>>> I thought reverse lookups worked their way down through the IP netblock
>>> assignments, and it would be up to the entity that ;owns' your IP address
>>> (i.e. your ISP) to resolve reverse lookups, or have some mechanism to
>>> delegate to you (latter is rare, AFAIK). Usually an ISP resolves it to some
>>> generated name like 12-34-56-78.static.ispname.com.
>> Well yes.  But it's "controls" rather than owns, in that when there's
>> a subassignment of a large block, that subassignment gets registered
>> with ARIN and the end network designates a DNS server for reverse
>> lookups.
>> The biggest issue is that CIDR blocks aren't supported in reverse
>> lookups particularly well, DNS is broken out by the octets of the
>> address, so if your block is smaller than a /24 you'll need to
>> cooperate on reverse lookups with the other networks in the /24.
>> How big is the block in question?  If it's a /24 or larger, does ARIN
>> show that block subassigned to your organization?  If yes, then make
>> your DNS host the name server for the reverse block and set things up
>> there.  If no, have your ISP register the subassignment.  If you have
>> a small block, use dig or nslookup to find out what is the DNS server
>> for reverse lookups in that block, and contact that group to add PTR
>> records for your addresses.
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