Ping check and timeout

David W. Hankins dhankins at
Wed Oct 28 16:58:44 UTC 2009

On Wed, Oct 28, 2009 at 10:41:30AM +0100, Thomas Marteau wrote:
> The first one is OK and you can see the 14 second offset between the
> DISCOVER and the OFFER and the second is the problem.
> Oct 28 10:09:30 instlinuxdsy dhcpd: DHCPDISCOVER from
> Oct 28 10:09:44 instlinuxdsy dhcpd: DHCPOFFER on to
> Oct 28 10:07:49 instlinuxdsy dhcpd: DHCPDISCOVER from
> Oct 28 10:07:49 instlinuxdsy dhcpd: DHCPOFFER on to
> Any idea where to start digging? Clients are identical in this example
> Windows XP 32 bits.

If the lease is static, or if the lease's CLTT is less than or equal
to 60 seconds ago, the server doesn't perform a ping check.

There's no config knob to adjust this behaviour, if it's not doing
what you want you'd have to look in server/dhcp.c and search for

I've always thought the CLTT check was pretty bogus but I wasn't
sure what I'd replace it with (current binding state != active?
this removes false positives but can have false negatives).

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
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 197 bytes
Desc: not available
URL: <>

More information about the dhcp-users mailing list