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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: RFC 974 - Mail Routing and the Domain System
On Tue, 15 Sep 1998, Studded wrote: > Michael J. Maravillo wrote: > > 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 [email protected], > which seems to be back up and running. One small detail that you seem to have left out. If you use solution number 2 I believe the following will happen. Assuming for whatever reason 10.0.0.2 goes down. SMTP1 attempts to send mail to domain.com Domain.com's DNS server says that all mail goes to mx.domain.com and says that mx.domain.com points to 10.0.0.2. At this point, SMTP1 can not send any mail to domain.com until cached zone for domain.com expires on SMTP1 at which point, SMTP1 will requery ns.domain.com and may or may not get a different address for mx.domain.com I'm not sure as to the first scenario, but I believe from my own experience sending mail to domains with multiple mail handlers (ie mx1.domain.com mx2.domain.com etc.) that it will send to different servers each time it hits them. Once again, I do NOT know this to be true, this is just what I seem to have experienced. Also, I think this type of thing would be better posted on [email protected] not a bind list since it relates to Sendmail operation as well as bind.. Tim ---------------------------------------------------- Timothy M. Wolfe | Why surf when you can Sail? [email protected] | Join Oregon's Premier Sr. Network Engineer | Wireless Internet Provider! ClipperNet Corporation | http://www.clipper.net/ ----------------------------------------------------
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