🚀 go-pugleaf

dhesi@rahul.net (Rahul Dhesi) writes:

>    However, you can have an
>    additional A record that gives company.uk the same IP address as
>    foo.company.uk.  If you order the A records appropriately, the
>    primary name can be foo.company.uk, but mail will still get
>    correctly delivered when addressed to company.uk.

What do you do with PTR records in this case?  Is it legal to have
multiple PTR records for a single Internet address?  If not, then mapping
company.uk to its IP address and reverse-mapping it back will give you
foo.company.uk.  I suspect some software will get unhappy about this.
(Actually, maybe not - I thought log_tcp would be one of the unhappy
ones, but it doesn't seem to mind as long as IP->name->IP gets back the
right address).

> c: Several MX records are often assumed to be more reliable for mail.
>    However, it's not clear to me that they buy you much.  Presumably if
>    foo.company.uk is down, mail will remain queued for it at one of the
>    MX hosts.  It might as well just remain queued at the sending host.

If the mail is actually delivered on foo, that's true; but if foo uses an
alias file to deliver it to the users' real mailhosts, then the backup MXs
can do the same, and get it delivered even when foo is down.

Besides, if the sending site is one that's not always up, you risk having
the mail delayed longer because the sender happens to be down when foo
comes back up.  The backup MXs are presumed to be up all the time.

>    A disadvantage is that people won't be able to telnet directly to,
>    or ftp directly from, company.uk.   Alternatives a and b don't
>    have this disadvantage.

For ftp, it seems like there's a growing tradition for having a CNAME for
ftp.company.uk pointing to the ftp server.

-- 
Tom Fitzgerald   Wang Labs       fitz@wang.com   "I went to the universe today;
1-508-967-5278   Lowell MA, USA                   It was closed...."