On Fri, Jun 25, 2004 at 04:05:56PM -0400, Mark Haney wrote: > I'm having a discussion with my boss over reverse DNS and I want to know > if my logic is correct. Who exactly resolves the reverse DNS queries? I > say it's the name server that serves up the regular DNS, but my boss > insists it is our ISP which isn't our primary DNS provider. Is there any > DNS FAQ's that explain this. I thought I knew how this worked, but now > I'm confused. Your boss is probably closer to right. Unless your ISP has delegated the reverse zone to you, then they probably control the reverse look-ups. It COULD be the same name server if you had both your forward domain and your reverse pointer zone in the in-addr.arpa. zone served by the same name server, but nothing requires it. But it doesn't HAVE to be your ISP either. They can delegate it to you, generally if you have a big enough block (/24 or better). Blocks of /25 or smaller get stickier to delegate and the ISP probably would prefer to manage it themselves. To reverse lookup an IPv4 address, you reverse the octets and append the .in-addr.arpa. domain to it and do a type PTR lookup (which "host" does implicitly when you give it an IPv4 address). [mhw@alcove mhw]$ host alcove.wittsend.com alcove.wittsend.com has address 130.205.12.10 [mhw@alcove mhw]$ host 130.205.12.10 10.12.205.130.in-addr.arpa domain name pointer alcove.wittsend.com. Sooo... Who has the name servers for those zones (drop the last component and look up the NS records): [mhw@alcove mhw]$ host -t NS wittsend.com. wittsend.com name server banshee.wittsend.com. wittsend.com name server ehecatl.iss.net. wittsend.com name server ns.commandcorp.com. [mhw@alcove mhw]$ host -t NS 12.205.130.in-addr.arpa 12.205.130.in-addr.arpa name server banshee.wittsend.com. 12.205.130.in-addr.arpa name server ns.commandcorp.com. Not quite the same. Close, in my case, since I do control both the domain and the netblock so I control both the forward and reverse lookup zones. IPv6 reverse lookups get even groddier... Reverse the nibbles... All 32 of them... > -- > Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt. > Mark Haney > Network, Database and Systems Administration > DoctorDirectory.com Inc. Mike -- Michael H. Warfield | (770) 985-6132 | mhw@xxxxxxxxxxxx /\/\|=mhw=|\/\/ | (678) 463-0932 | http://www.wittsend.com/mhw/ NIC whois: MHW9 | An optimist believes we live in the best of all PGP Key: 0xDF1DD471 | possible worlds. A pessimist is sure of it!
Attachment:
pgpUU4GxhBtdW.pgp
Description: PGP signature
