Date: Fri, 23 Oct 2009 12:18:53 -0400 From: Sean Cavanaugh <millenia2000@hotmail.com> To: "freebsd-questions@freebsd.org" <freebsd-questions@freebsd.org> Subject: FW: DNS Question Message-ID: <BAY126-W12706A30D1794B2638ABC3CABD0@phx.gbl> In-Reply-To: <200910231717.AA243925902@mail.Go2France.com> References: <200910231717.AA243925902@mail.Go2France.com>
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> Date: Fri=2C 23 Oct 2009 17:17:48 +0200 > From: lconrad@Go2France.com > To: freebsd-questions@freebsd.org > Subject: Re: DNS Question >=20 > > > >All true=2C and I did not do a very good job of explaining it. My issue= =20 > >was that we have requests to use a CNAME for the domain record. Such as= =20 > >this. > > > >example.com CNAME otherdomain.com > >www.example.com CNAME otherdomain.com > > > >I was taught this was not good form >=20 > worse=2C it's illegal. how is this illegal? if you are residing your domain on a hosting service= =2C this makes sense to me. Granted its bad form and should have an A recor= d to the host for the main domain record=2C but if i had control over "othe= rdomain.com" and not "example.com" and had to change the IP address=2C "exa= mple.com" would be dead until i was able to reach the owner of that domain = and have them change their DNS info.=20 =20 =20 > =2C but allowed. I can deal with it.=20 > >But what of having a SOA record for example.com=2C no A or CNAME record= =20 > >for the TLD example.com=2C only hosts such as www=2C ns1=2C ftp=2C etc. > > > >I tried it an it seems to work fine=2C but doesn't look proper to me. Th= en=20 > >again I remember when CNAME were considered evil. >=20 > CNAMEs are still evil=2C unless=20 > 1) no other solution exists and=20 > 2) the user knows how to use CNAMEs (rare). >=20 > Len >=20 there is nothing that says you HAVE to have your tld labled in DNS. you wou= ld just run into issues if someone types http://example.com into their web = browser and not get a result in DNS. =20 =20 to clarify on CNAME's a bit better. CNAME's are nothing more than DNS alias= es. the reason you do not want to overuse them is that you could potentiall= y create a loop if you are not careful =20 www.site1.com CNAME www.host1.com. www.host1.com CNAME www.site1.com. =20 syntactically=2C this is correct but would cause an infinite loop until a t= imeout occurred on your computer. =20 also you want to limit how many weird names you get associated to one box. = it makes sense if you want www.example.com to point to your web server=2C w= hich you may have officially called "srvWeb"=2C but looking at things like = a mail server=2C would you rather only have the entry: =20 mail.example.com CNAME srvMail.example.com. =20 or have to edit this: =20 pop3.example.com CNAME srvMail.example.com. smtp.example.com CNAME srvMail.example.com. imap.example.com CNAME srvMail.example.com. =20 The other interesting side would be reverse DNS lookups. Only one record wo= uld be returned=2C and most likely would be the original A record. A nice e= xample of this is doing a basic "ping -a www.yahoo.com" which you get back = that it is resolving "www-real.wa1.b.yahoo.com". =
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