Multi-Master and NOTIFY

[Mark Andrews]

> Folks,
> 
> We are running slaves with multi-masters for some of our clients. Our 
> slaves are running on BIND 9.3.1. Consider the following typical scenario:

	Why are they still running BIND 9.3.1?
 
> Client has two master servers, 192.168.1.25 and 192.168.1.26, both of 
> which are configured as masters in our slave zone declaration; masters { 
> 192.168.1.25; 192.168.1.26; }.
> 
> There have been cases where the zone file on 192.168.1.25 is not correctly 
> being updated by the zone generator, so as updates occur, the zone's 
> serial number is not being incremented. However, the second master, 
> 192.168.1.26, is properly updating and has incremented it's serial number.
> 
> When this happens, our slave servers will receive a notify from 
> 192.168.1.26, will queue a refresh check, and then start to check the 
> masters in order. When BIND queries 192.168.1.25, it discovers that it is 
> up to date from 192.168.1.25's point of view, and stops processing.

	That is incorrect.  See lib/dns/zone.c:refresh_callback().

> Is there any way to force BIND to search all masters to get updated to the 
> serial number it received in the NOTIFY packet? Or can I force BIND to 
> zone transfer from the server which it received the NOTIFY from?

	Named already checks all the masters.
 
> According to Paul Vixie on 2005-02-02 14:56:38, it should be doing this:
> 
> "it will try them all, transfer only from a master offering the best 
> currently available serial number.  this is tricky given "sequence number 
> arithmetic" and 32-bit rounding."
> 
> However, I do not see this happening. As a side note, the serial numbers 
> being used are not on any sort of 32-bit rounding boundary.
> 
> Can anyone shed some light on this? I haven't seen anything in the 
> archives that point to this issue.
> 
> Thanks,
> Tom Daly
> 
> -- 
> Thomas J. Daly
> tom at dyndns.com
> Dynamic Network Services, Inc.
> http://www.dyndns.com/
> 
> 
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org