Smarthost Failover - WAS RE: [Mimedefang] SMTP mailertable questi on

[Cormack, Ken]

> If you (or any other of the list readers) try this, can you post a summary
> of how it works?  I'm still some time away from implementing this, but am
> quite curious to hear other's feedback.

Several days ago, a somewhat off-topic discussion thread on this list was
going on, about how to have an internal mail gateway failover from one
defined smarthost, to another.  The following link suggested a method that
could be tried.
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&c2coff=1&th=552f
bc7b7c4525f0&seekm=b8ue8i%241plj%244%40hedeland.org&frame=off

Rather than defining the smarthost by name in the sendmail.mc file like
this...
define(`SMART_HOST', `mail01.mydomain.com')

... and having to either change the entry (and rebuild sendmail.cf) or
change the address to which the name resolves, we tried the following, using
the litteral IP addresses of our primary and secondary external gateways,
like this...

define(`SMART_HOST', `[192.168.1.1]:[192.168.1.2]')

Failover was immediate, when I stopped sendmail on the primary smarthost.
My internal gateway immediately began routing mail automatically via the
secondary machine.  I saw two different emails in the log, at the instant I
shut down my primary gateway.  One of the emails was the last to be handed
to the primary before the primary was shut down.  The next was a different
email, the first to be routed to the secondary machine.  The timestamps on
the two messages were the same, down to the second.  The auto-failover
happened just that quickly.

The moment I brought the primary back online, my internal gateway
immediately began routing mail to that host again.

I was asked to post a summary of any success.  Here it is.  :)

KEN CORMACK, RHCE
Sr. UNIX Systems Analyst,
    Open Systems Group
Sr. Software Analyst,
    TSG Midrange Systems Group
AFFILIATED COMPUTER SERVICES, INC.
    557 E. Tallmadge Ave., Akron, OH  44310
    mailto:kcormack at acs.roadway.com
    mailto:ken.cormack at acs-inc.com
    Phone: (330) 643-6372
    Fax: (330) 643-6367
    Pager: (800) 946-4646 Pin 1412819

"If that that is 'is' is that that is not 'not is', is that that is 'not is'
that that is not 'is'?  It is!" - Ken Cormack

"Sendmail administration is not black magic.  There are legitimate technical
reasons why it requires the sacrificing of a live chicken." - Unknown