Date: Fri, 23 Oct 2009 17:15:09 +0200 From: "Len Conrad" <lconrad@Go2France.com> To: <freebsd-questions@freebsd.org> Subject: Re: FW: DNS Question Message-ID: <200910231715.AA1453851224@mail.Go2France.com>
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---------- Original Message ---------------------------------- From: krad <kraduk@googlemail.com> Date: Fri, 23 Oct 2009 15:56:40 +0100 >2009/10/23 Sean Cavanaugh <millenia2000@hotmail.com> > >> >> >> >> > Date: Fri, 23 Oct 2009 08:30:08 -0400 >> > From: dave.list@pixelhammer.com >> > To: freebsd-questions@freebsd.org >> > Subject: DNS Question >> > >> > Good morning. >> > >> > I have been asked by my co-workers and sales why I always create a A >> > record for new domains we host instead of a CNAME. >> > >> > The issue I run into lately with some domains is that a client has a >> > website with a industry host such as frank.relator.com and he wants to >> > have DNS point www.frank.com to frank.relator.com with a CNAME. The >> > client does not want an A record for frank.com. >> > >> > Somewhere, in a class far far away, I was taught a DNS zone had to have >> > a A record to function properly. I can't seem to locate anything in the >> > RFCs. >> > >> > Am I wrong? >> > >> >> >> I think you are confusing basics of DNS records. you are partially correct >> in that a DNS zone needs an initial A record to be able to translate a name >> to an IP, but there is nothing wrong about setting up a CNAME to point to a >> record in a different zone instead. you just cannot do a zone that has a >> CNAME only that does not at some point to a valid A record. CNAMEs are >> forwarders only whereas A records are actual lookups. >> >> for proper way to set this up.... >> >> The A record would be assigned for the main name that you want to associate >> to an IP address. >> The CNAME record just relates a different name to that original name. this >> allows you to change the IP address of the server and only have to update >> the original A record instead of every DNS record for that server. >> >> for small number of vhosts, this would not really be an issue, but imagine >> if you were hosting a couple hundred vhosts from a single IP and then had to >> change that IP because you switched your ISP. It would take you a LONG time >> to update them if they were all A records, but only a couple of seconds if >> you had it properly set up as CNAME's >> >> www.bobshosting.com A 192.168.0.1 >> www.vhost1.com CNAME www.bobshosting.com. >> www.vhost2.com CNAME www.bobshosting.com. >> www.vhost3.com CNAME www.bobshosting.com. >> www.vhost4.com CNAME www.bobshosting.com. >> >> >> >> -Sean >> >> >> _______________________________________________ >> freebsd-questions@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-questions >> To unsubscribe, send any mail to " >> freebsd-questions-unsubscribe@freebsd.org" >> > >I try to use CNAMES as much as possible, for one very good reason. If say I >have web server with 1000 vhost on it. I have one A record for the server >and all the cnames point at that A record. Now i need to change the ip of >the server. I update the A record and add a reverse record and im done. IF I >had done it your way with all A records I would now have to go and edit >another 1000 records. Even worse if some of these domains are not under my >control I have to go and liaise with customers, or other third parties, and >it becomes a complete mess. The chances of me convincing them all and >coordinated it correctly are minimal 8( domains sharing records is better handled by $INCLUDE $INCLUDE /path/db.ttl, which contains $TTL 6h $INCLUDE /path/db.ns, which contains @ ns ns1.domain.tld. @ ns ns2.domain.tld. $INCLUDE /path/db.www, which contains @ a ip.ad.re.ss www a ip.ad.re.ss etc. Changing an include file changes all the zone files that include it, giving enormous leverage, while removing the extra query required to resolve a CNAME to canonical. Len
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