[CentOS] Split dns issues

Jason Pyeron jpyeron at pdinc.us
Mon Aug 3 16:07:35 UTC 2009

> -----Original Message-----
> From: centos-bounces at centos.org 
> [mailto:centos-bounces at centos.org] On Behalf Of Filipe Brandenburger
> Sent: Monday, August 03, 2009 10:40
> To: CentOS mailing list
> Subject: Re: [CentOS] Split dns issues
> Hi,
> On Mon, Aug 3, 2009 at 10:27, Jason Pyeron<jpyeron at pdinc.us> wrote:
> > My worry is the A record for the outsourced mail service is 
> out of our 
> > control, if it were to change it would be catastrophic.
> Well, if you *must* use a name like mx.google.com for your 
> MX, you could also set up an mx.google.com domain as 
> authoritative in your domain, and then add an "A" record with 
> your internal mail server there... It's not beautiful, but it 
> should work.

I think this is a perfect solution as weighed against every thing else.

> Another alternative is to use "includes" in BIND, that way 
> you could have "views" for your pdinc.us zone, then on both 
> of them you would only have the MX record (which would be 
> different on each of them) and maybe the SOA record (but you 
> could also decide to keep that on the included file) and then 
> an include to a file that contains the bulk of the records 
> for the zone. Would that solve your problem managing views 
> for that zone?

Too messy, as there are many changing records, and some are already klobbered as
described above and in previous emails.

> > I like the idea about the cname. Can a cname be used as a 
> host for a MX record?
> Not according to the RFCs, but in practice it does work. 
> Beware that you might stop receiving e-mails from very old 
> and very buggy e-mail servers though (like maybe Exchange 5 
> or very old Lotus Notes, but I don't think anyone still uses those.)

Doh. We use Exchange 5.5 SP4. (don't ask)

> > The other fear is the outsourced (showing ignorance on SMTP here) 
> > might react badly to the client making a connection to a 
> server with a 
> > name different than they expected, as it looks like they 
> are doing a name based virtual hosting.
> I don't think so, since SMTP only uses the name of the MX 
> server for the TCP connection to the server's IP, nothing in 
> the protocol later will use that name again. Virtual hosting 
> is usually done by having the server accept e-mails to any of 
> those e-mail domains on the same server.

I guess they are doing the weird naming thing so they can shuffle servers

> HTH,
> Filipe
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- Jason Pyeron                      PD Inc. http://www.pdinc.us -
- Principal Consultant              10 West 24th Street #100    -
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