Date: Fri, 28 Feb 1997 16:37:17 -0800 (PST) From: Dan Busarow <dan@dpcsys.com> To: Adrian Gonzalez <agonzalez@starbase.globalpc.net> Cc: freebsd-isp@FreeBSD.ORG Subject: Re: DNS question Message-ID: <Pine.UW2.3.95.970228160757.16033F-100000@cedb> In-Reply-To: <Pine.BSF.3.91.970228162710.15168A-100000@starbase.globalpc.net>
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On Fri, 28 Feb 1997, Adrian Gonzalez wrote: > I need to set up 2 different domain in the same class C network, but in > different subnets... for example (these are not the real addresses, of > course) > > 128.1.2.0 to 128.1.2.31 - first subnet > 128.1.2.32 to 128.1.2.63 - second subnet > [ ...] > > What would the reverse entries look like? > > primary 2.1.128.in-addr.arpa foo.rev (??) primary 2.1.128.in-addr.arpa db.128.1.2 Using my preferred naming, the zone is for the address space, not the domain. In the reverse files you need to have an entry for the name servers you are delegating subnet space to like: 0 IN NS ns.foo.com. 32 IN NS ns.bar.com. These are *not* the addresses of the name servers, this says that the 0 subnet has name server ns.foo.com and the 32 subnet has name server ns.bar.com. Now comes the fun part. For *every* delegated IP address you need entries like this: 1 CNAME 1.0.2.1.128.in-addr.arpa. 2 CNAME 2.0.2.1.128.in-addr.arpa. 3 CNAME 3.0.2.1.128.in-addr.arpa. 4 CNAME 4.0.2.1.128.in-addr.arpa. 5 CNAME 5.0.2.1.128.in-addr.arpa. 6 CNAME 6.0.2.1.128.in-addr.arpa. See how we gave them an extra octet? Actually, since these are domain names, not IP addresses, we have just added another level to the domain. So when I do a reverse lookup on 128.1.2.1 BIND does this 1) get the CNAME 1.0.2.1.128.in-addr.arpa 2) drop the left most part of the domain name and get 0.2.1.128.in-addr.arpa. 3) lookup 0.2.1.128.in-addr.arpa and get the NS entry pointing at ns.foo.com. 4) direct the query to ns.foo.com The reverse files ns.foo.com maintains look normal, ie 1 IN PTR ns.foo.com. 2 IN PTR mail.foo.com. For addresses outside of the delegated portion (64-255 here) you have normal entries. If you are reserving this C for subnets only (good idea) then the only entries you would need would be for your side of any gateways. If you get a customer who needs a subnet but can't (won't) handle reverse DNS (Macs can't) then you maintain their entries in the same file with "normal" PTR records. For a full discussion see draft-ietf-cidrd-classless-inaddr-01.txt at your favorite IETF draft repository. Dan -- Dan Busarow 714 443 4172 DPC Systems / Beach.Net dan@dpcsys.com Dana Point, California 83 09 EF 59 E0 11 89 B4 8D 09 DB FD E1 DD 0C 82
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