On 11-Jan-00 at 18:16:40 Dave C. wrote:
> One thing that CNAMES does allow is for grouping/seperation..
>
[...snipped...]
> CNAMES provide a way of doing this by mapping 'logical' or 'functional'
> hostnames onto real hostnames. I dont think that was its original
> purpose, but there isnt anything else that does..
>
You are actually right in our case, and that is in fact one reason why I
asked the original question. Internally we do use a CNAME for the mailhub
simply because users ask which POP server to use, which mailhub (smtp
system), etc. During the disaster recovery procedures we found that we would
have to rename or re-IP the system and that, especially for external users,
they would end up using the wrong IP address or name. (Didn't explain that
too well, but if you have to 'move' your mailhub by name and IP address
(since you still want the old one on-line whilst it is being rebuilt), then
all the users have the wrong name/IP for the live mailhub. Secondly, asking
the users to change (reconfigure) their software (web clients, mail clients
and whatever) for the new IP address/name is not generally a good idea. And
then, of course, to change it back :-) )
It was easier to assign it an alias and let everyone know that. We then
simply change the one CNAME entry. The current DNS zone files are built by a
convoluted procedure. If that gets sorted out then, yes, I would rather use
the canonical name.
On 11-Jan-00 at 18:35:59 Gyan Mathur wrote:
> Isn't it as easy to change the A record?
True generally I guess, just not in our case :-(
On 11-Jan-00 at 18:54:06 Dean Brooks wrote:
> While the above solution (whether implement as shown or in zone file
> macros) may be elegant, it will eventually cause you nightmares when
> one of your users/customers complains of {un|mis}delivered mail.
>
Hmm, well we've run this for some time now and not had a single complaint or
problem (that we know of!) :-) That includes our own internal departments
using a variety of MTA's :-)
> Not to mention the absolute horrors of what happens when people
> reference CNAMEs in NS records. That's definitely not a pretty sight.
>
Ah, yes. We don't do this, but the (bad) results of it seem to appear much
quicker for those sites that do than us using a CNAME in an MX record.
John.
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