Date: Thu, 11 May 2000 11:49:06 -0400 From: Mitch Collinsworth <mkc@Graphics.Cornell.EDU> To: "Marius Vincent" <mvincent@elcb.co.za> Cc: "freeBSD-Questions" <freebsd-questions@FreeBSD.ORG> Subject: Re: Block and reverse DNS. Message-ID: <200005111549.LAA86229@larryboy.graphics.cornell.edu> In-Reply-To: Message from "Marius Vincent" <mvincent@elcb.co.za> of "Thu, 11 May 2000 14:22:50 %2B0200." <NEBBJNFFELDAHIBIGIAMOEPMCCAA.mvincent@elcb.co.za>
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>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
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