Mail Server (DNS) Migration

[Kevin Darcy]

Brad Knowles wrote:

> At 10:04 PM -0400 4/20/01, Kevin Darcy wrote:
>
> >  You could try replacing that CNAME with 2 A records, one for each address.
> >  If the clients are smart enough, they'll fail over automatically after a
> >  short delay. This delay may even be configurable.
>
>         Problem is, PC clients *aren't* smart enough to do that -- they
> only ever use the first IP address they are told about, and never
> fail over to the second.

I've tested several web browsers and found them to be capable of A-record
failover. Admittedly, I haven't done the same testing for POP3/IMAP clients
(since we don't use those here as a rule), but I can't imagine that the result
would be that different, since many if not most POP3/IMAP clients are integrated
*into* web browsers these days, and the two components should presumably be
using common networking routines.

>         This is why you need load-balancing switches and/or
> application-layer proxies to hide that kind complexity and make it
> appear that there is only ever one machine that they're talking to.

This seems like overkill, just to facilitate a (presumably) one-time mailserver
migration...


- Kevin