From owner-freebsd-questions Thu May 11 8:49:34 2000 Delivered-To: freebsd-questions@freebsd.org Received: from larryboy.graphics.cornell.edu (larryboy.graphics.cornell.edu [128.84.247.48]) by hub.freebsd.org (Postfix) with ESMTP id 5EB5137B574 for ; Thu, 11 May 2000 08:49:30 -0700 (PDT) (envelope-from mkc@larryboy.graphics.cornell.edu) Received: from larryboy.graphics.cornell.edu (mkc@localhost) by larryboy.graphics.cornell.edu (8.9.3/8.9.3) with ESMTP id LAA86229; Thu, 11 May 2000 11:49:06 -0400 (EDT) (envelope-from mkc@larryboy.graphics.cornell.edu) Message-Id: <200005111549.LAA86229@larryboy.graphics.cornell.edu> To: "Marius Vincent" Cc: "freeBSD-Questions" Subject: Re: Block and reverse DNS. In-Reply-To: Message from "Marius Vincent" of "Thu, 11 May 2000 14:22:50 +0200." Date: Thu, 11 May 2000 11:49:06 -0400 From: Mitch Collinsworth Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG >Could somebody please tell me how reverse lookups take place in theory. >As far as I know it works like this: > >If you do a nslookup on 111.111.111.111 then your dns server contacts the >root servers and requests a dns server ip for the class A address 111.0.0.0, >then it askes the dns server of 111.0.0.0 to look for 111.222.0.0.0 in its >records and the same for 111.111.111.0 >and once again the same for the last step that the last DNS server will look >in it's ptr records and return a address of 111.111.111.111 pointing towards >foo.bar.com > >right???? or wrong?? hmm, well you're sort of on the right track here, but your explanation is wrong. When you "nslookup 111.222.333.444" your request is converted into a request for a PTR record for "444.333.222.111.in-addr.arpa." From there, all normal lookup rules apply, i.e. first lookup "arpa.", then "in-addr.arpa.", then "111.in-addr.arpa.", etc. Basically, there is nothing special about reverse lookups except for converting the IP address into in-addr.arpa notation before starting. -Mitch To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message