On Wed, Apr 02, 2003 at 09:22:31PM -0800, Paul Johnson wrote: > (Please reply to the list as others may run into this problem, too) > > On Wed, Apr 02, 2003 at 10:32:07PM -0500, Stephen Touset wrote: > > Is that a limitation of ddclient? I've tried inputting the values > > manually on their webpage, and it works perfectly. > > Hmm, that's odd... I'd have to look that up but I think MX's have to > point to A's by the RFCs. Anybody else have input on this? I'll try :-) *rfc pedant hat on* [rfc 1035, 3.3.9] "MX records cause type A additional section processing for the host specified by EXCHANGE." Thus, one can conclude that the authors of the DNS protocol intended that MX records should refer to A records. This does of course incur the cost of an additional lookup on the A record returned. There's been a lot of debate as to whether MX records can indeed return an IP address rather than an A record. Some people have set up their DNS this way, in violation of the RFC. In my opinion, it seems prudent to process these replies (you know, be liberal in what you expect, but conservative in what you send). If an MX record returns IPs instead of A records, it saves one lookup, though you forego the possibility of any round-robin DNS load-balancing. Personally, I think it is best to abide by the RFC and make sure that your MX records, if present, refer to A records. -- Nathan Norman - Incanus Networking mailto:email@example.com A young man wrote to Mozart and said: Q: "Herr Mozart, I am thinking of writing symphonies. Can you give me any suggestions as to how to get started?" A: "A symphony is a very complex musical form, perhaps you should begin with some simple lieder and work your way up to a symphony." Q: "But Herr Mozart, you were writing symphonies when you were 8 years old." A: "But I never asked anybody how."
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