DHCP failover lease balancing with nearly saturated pools

David W. Hankins David_Hankins at isc.org
Thu Jan 29 00:53:43 UTC 2009


On Wed, Jan 28, 2009 at 04:53:37PM -0600, Jack Kielsmeier wrote:
> The primary server hands out leases, and the pools on busy subnets are
> balanced every 5 minutes or so. When there is only one lease left, the
> secondary won't balance that lease over to the primary.

This is because there's an odd number of leases remaining.  If each
server opted to 'round up' from 0 to 1 lease to give away to the
peer, then in this (and other) cases, they would never stop giving 1
lease to each other to try and balance the pool every go round.

Failover isn't really well designed for the case where the servers
don't see all the broadcast traffic, I don't really have an easy
answer for that.

-- 
David W. Hankins	"If you don't do it right the first time,
Software Engineer		     you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins
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