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Creighton MacDonnell wrote:
> What I meant is that GnuDIP maintains two MX records. Each is either
> present or not present, independently of each other. One is the the
> user's own dynamic domain name (if the user selects "Backup Mail
> Exchanger"). The other is the one the user can type in (which I called
> "foreign").
Ah! Now I understand what the semantics of that button are supposed
to be. Hmm. How about the case where the user has both a primary
and secondary MX for his host, but neither are supposed to be the
host itself? (He has email going to his FQDN, but does not run
the MTA/MDA himself?)
>> - permitting an update to result in multiple 'A' records
>> rather than just one, thus winding up with entries
>> like this:
>> host.example.com. IN A 192.168.1.10
>> IN A 10.10.5.18
>> IN MX 100 mx1.example.com.
>> IN MX 200 mx2.example.com.
>> Think of the case where you have a multiply-homed site
>> where at least one of the interfaces is on dhcp. The
>> "fix my particular problem" case is allowing for one
>> IP via dhcp, and one IP which is static. The general
>> case would be two or more, any of which can be dynamic
>> or static.
>
> I am not sure I follow the details of this scenario.
There's a few variations on the theme, but consider this one
(which exists today), simplified somewhat:
One of my users is a hobbiest who has a routable /24 with a
residential DSL upstream. It's usually good, but sometimes
takes an outage. It's a bit annoying but he doesn't want the
expense or administrative hassle of running a proper multihomed
network, which would imply BGP et al. Instead, he has gotten
a 2nd connection by getting a residential cable modem from another
provider, which provides a single IP via dhcp. Enter GnuDIP.
The machine on the cable modem and the one on his DSL modem act
as gateways for the network.
Now the 2nd link is good for acting as an ssh gateway, and with
appropriate magic we can also use it for an MX. There are a
few services which aren't as convenient to set up for redundancy,
though, such as HTTP (which I will use as the example although
there are other services which fall into the same category).
The web servers on the /24 do virtual hosting. As a consequence
(the reasons of which I shall not go into here) if one were to
provide multihomed services for both www.example.com and
www.another.com (where they are on the same server), then one
would need the following records:
www.example.com IN A 192.168.1.10
IN A 10.10.5.18
www.another.com IN A 192.168.1.10
IN A 10.10.5.18
In other words, both hostnames need two 'A' records, and
you can't fake it out with CNAMEs. As far as I can see,
GnuDIP will only permit a single 'A' record for a given
host, thus my original comments.
I know that in this scenario there are potential routing issues
(such as what happens if the packets come in on one interface
and out on another), but that is beyond the scope of GnuDIP.
It's ugly, but not intractable. BTW, the web server itself
is only single-homed, but the network via its routers is
multiply-homed.
Does that clarify things at all?
Are you having nightmares yet? :)
--
Devin Reade <[EMAIL PROTECTED]>
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