Failover and Load Balancing

David W. Hankins dhankins at
Fri Nov 20 00:19:12 UTC 2009

On Wed, Nov 18, 2009 at 10:24:44AM -0500, Jason Frisvold wrote:
> 	We have made additional progress with our DHCP failover setup.  By
> increasing the "load balance max seconds" parameter, it appears that
> only one of the two servers is responding to requests now.  Failover
> still works, but I'm not seeing the "load balanced" messages in the
> logs.  Is this normal?

It is normal but worrisome; you want to answer your clients when they
send their first message (and secs = 0).  :(

It is really hard to say what could be the cause of clients having to
retransmit; network drops, spanning tree holding their ports down
before they can get their first DHCPDISCOVER out, and even (heaven
forbid) slow or overloaded DHCP servers...

> 	Are there any tools out there for testing this sort of scenario?  I'm
> looking for something that can properly send DHCPDISCOVER packets,
> respond appropriately by accepting the lease, etc.  Anyone know where I
> can find such a thing?

I remember someone wrote a DHCP packet sender/receiver tool, and I've
been meaning to get it into contrib/.  The process keeps getting stuck
when I get distracted by shiny objects and balls of yarn.

You might look for 'dhcping', I don't know if it is still available or

David W. Hankins	BIND 10 needs more DHCP voices.
Software Engineer		There just aren't enough in our heads.
Internet Systems Consortium, Inc.
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