Load balancing outgoing mail relay

Charles Trevor ct.lists at qgsltd.co.uk
Wed Jan 17 17:23:11 UTC 2007


freebsd wrote:
>> This (multiple A records) works for me, at least approximately. Both
>> Bind and MS DNS will round robin when multiple A records exist for the
>> same hostname. What is your setup?
> 
> FreeBSD 6.2 with Sendmail (initially) and now postfix.
> MS DNS with round robin (and TTL set to 0 on the records).
> Resolving with nslookup gives something like:
> smarthost.domain.tld
> 192.168.0.1, 192.168.0.2, 192.168.0.3
> 
> If I kill 192.168.0.1 then it goes on the second one. But this is 
> failover, and I need (approximately) load balancing.
> I understand this is related to the MTA and not to the OS, but hopefully 
> someone solved this problem using Sendmail or Postifx that are both used 
> on FreeBSD.
> Thanks
> 

What happens if you do multiple dig/nslookups for smarthost.domain.tld. 
Are the records returned in a different order each time? If not the 
problem may be at the NS.

Charlie


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