Date: Fri, 23 Oct 2009 13:49:19 +0100 From: Matthew Seaman <m.seaman@infracaninophile.co.uk> To: DAve <dave.list@pixelhammer.com> Cc: 'User Questions' <freebsd-questions@freebsd.org> Subject: Re: DNS Question Message-ID: <4AE1A64F.1000405@infracaninophile.co.uk> In-Reply-To: <4AE1A1D0.8060402@pixelhammer.com> References: <4AE1A1D0.8060402@pixelhammer.com>
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This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigD55BD1E905DA0180AD30608D Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable DAve wrote: > Good morning. >=20 > I have been asked by my co-workers and sales why I always create a A=20 > record for new domains we host instead of a CNAME. >=20 > The issue I run into lately with some domains is that a client has a=20 > 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=20 > client does not want an A record for frank.com. >=20 > Somewhere, in a class far far away, I was taught a DNS zone had to have= =20 > a A record to function properly. I can't seem to locate anything in the= =20 > RFCs. >=20 > Am I wrong? Yes, you're wrong. In terms of web service, you can use either an A record or a CNAME record= to provide the address part of a site's URL[*]. As far as the web server= is concerned, it looks for the 'Host=3D' line in the HTTP packet to decide w= hat name-based VHOST to dispatch the query to internally, and doesn't necessa= rily do any DNS lookups at all. Web clients just do a gethostbyname(3) or get= addrinfo(3) call to resolve the site name into an IP, and anything suppo= rted by those (/etc/hosts, NIS, LDAP, DNS) will do the trick. In terms of the DNS a 'Zone' is a delegated block of the name space under= a single administrative control. Typically with BIND this maps onto a si= ngle 'Zone file' containing all of the DNS resource records for the zone. The= only records a zone *has* to have are: * 1 SOA record, with the zone serial number * Some number of NS records giving the nameservers for the zone. It's perfectly permissible to have a zone that doesn't contain any A records (or AAAA records) and in fact, reasonably common: reverse domains= generally contain mostly PTR records.=20 Cheers, Matthew [*] Possibly others, but A and CNAME are the vast majority. Being able t= o use SRV for webservers would be cool. --=20 Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard Flat 3 PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate Kent, CT11 9PW --------------enigD55BD1E905DA0180AD30608D Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.13 (FreeBSD) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEAREIAAYFAkrhplYACgkQ8Mjk52CukIyFsgCeI7sHpEnPeFHGWyk7cXYtEK2r 4NkAoIjt3o8YeWlKbjQ1vsYvRCOBOsxJ =1xjM -----END PGP SIGNATURE----- --------------enigD55BD1E905DA0180AD30608D--
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