RFC 974 - Mail Routing and the Domain System

Tue Sep 15 20:39:03 UTC 1998

Michael J. Maravillo wrote:
> 
> Hello,
> 
> 'Just want to clarify something... is there a difference between:
> 
> domain.com. MX 10 mx1.domain.com.
> domain.com. MX 10 mx2.domain.com.
> domain.com. MX 10 mx3.domain.com.
> ;...
> mx1.domain.com. IN A 10.0.0.1
> mx2.domain.com. IN A 10.0.0.2
> mx3.domain.com. IN A 10.0.0.3
> 
> and:
> 
> domain.com. MX 10 mx.domain.com.
> ;...
> mx.domain.com. IN A 10.0.0.1
> mx.domain.com. IN A 10.0.0.2
> mx.domain.com. IN A 10.0.0.3
> 
> >From RFC 974:
> 
> "...Note that multiple MXs may have the same preference value.  In
> this case, all MXs at with a given value must be tried before any of a
> higher value are tried..."
> 
> Is the behaviour the same with the round-robined configuration?

	My imperfect understanding of how most mail agents handle MX records is
that with the first configuration, mx1 will always be tried first,
followed by mx2, etc. With the second configuration, a BIND server will
return the A addresses in an effectively random pattern, so load should
be distributed across the 3 servers. 

	For future reference you are better off asking at bind-users at vix.com,
which seems to be back up and running. 

Good luck,

Doug
-- 
***           Chief Operations Officer, DALnet IRC network          ***

"Yes, the president should resign. He has lied to the American people,
time and time again, and betrayed their trust. He is no longer an
effective leader. Since he has admitted guilt, there is no reason to put
the American people through an impeachment. He will serve absolutely no
purpose in finishing out his term; the only possible solution is for the
president to save some dignity and resign."

- William Jefferson Clinton, 1974