DHCP failover lease balancing with nearly saturated pools

David W. Hankins David_Hankins at isc.org
Wed Jan 28 21:56:02 UTC 2009

On Wed, Jan 28, 2009 at 01:48:15PM -0600, Jack Kielsmeier wrote:
> Currently, when the pools become nearly 100% saturated, the primary
> server throws out 'peer holds all free leases' errors. This is correct
> because the peer holds the final lease. Since I'm shipping all traffic
> to the primary server, that last lease will never be given out.

I don't know as of what version, but if the servers agree on the
lease states (no db synch. problems), then the secondary should know
that there are zero free leases and will over-ride the LBA

So the version you're running might be an issue.

The only place I'm not sure is if you've got a series of pools in a
given shared network, and some of them have ACL's applied that don't
match the client.

The other thing is that the peer should offer the lease if the client
has been (re)trying for more than 'load balance max secs (n);'.
Note that this is advertised by the client (in the BOOTP header 'secs'
field), so the servers don't have a lot of say about it, but most
clients put something useful there.

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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