maximum lease times?

[Chris Buxton]

On Apr 19, 2011, at 12:16 PM, Alan Buxey wrote:

> hi,
> 
> sorry for a rather bland question but does anyone know
> of any possible issues with slightly longer lease times and
> OS support?  I'm looking at a wierd issues where clients are
> just 'dropping' their IP rather than renewing. initial inspection
> found the DHCP config for the VLAN to have a lease tim eof 259200 (3 days)
> - the usual range we have is 86400 - so, rather knee-jerk reaction
> was taken - that VLAN was set to 86400 too (1 day) - but I was wondering
> if there were random OS issues that people have come across
> with clients...some war stories from the wounded? - in theory
> DHCP lease times can be inifite...or seconds rather than minutes..
> but the server is accessible - we see DHCP renewals , ACKs etc all through
> the day - even from other systems in the same LAN that other systems drop
> off from at same time-period.

I've seen lease times of up to a year appear to work as expected.

If other clients on the VLAN (getting similar leases) are working correctly, then I would guess there's an issue with the clients that are malfunctioning. Or there could be an issue with the leases they're given, possibly with the wrong gateway or some other setting that prevents unicast renewals at 50%. However, even with that, the broadcast renewal at 87.5% should still work, assuming the client performs this correctly.

After dropping their IP, do these clients get a new lease from scratch?

Chris Buxton
BlueCat Networks