how to force new leases (not renewals)

[Justin DeMaris]

One very unconventional trick we have used to push out lease changes is to do shut/no shut on the switch port interface. This only works for devices wired directly to the switch with no active amplification (hub, etc) in between but it makes windows and linux do a full new lease since it feels like it got unplugged
------Original Message------
From: Len Conrad
Sender: dhcp-users-bounces+justin.demaris=uconn.edu at lists.isc.org
To: Users of ISC DHCP
ReplyTo: Users of ISC DHCP
Subject: Re: how to force new leases (not renewals)
Sent: Jan 25, 2010 8:47 PM


>> We have what must be common situation: we want to change the IPs of 
>> the recursive DNS in our DHCPACK answers, and have done so, but 
>> Windows dhcp clients ask for renewals (keeping the old DNS IPs).
>
>On renew, the client should pick up changes in DHCP options including 
>the domain-name-servers option.

that's not happening.  After about 10 days of changing the DHCP server to the new IPs (12 hour lease), we are still getting a few 1000 IPs making recursive queries to the old DNS IPs. We know we don't have that many IPs not running DHCP.   At this rate, it will take weeks to have no DCHP clients using the new IPs.

It seems that Windows asks for renewal of its current lease, and isn't getting (or ignoring) a new set of lease params.

thanks
Len



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