Automatic remove lease from pool

Henrik Sterndorff Jessen hsj at
Wed May 23 19:28:27 UTC 2007


I am using dhcp to dish out fixed addresses to users. All users are
connected to cisco switch ports that act as a relay and therefore add
option-82 information to the dhcp query. I don't know the mac addresses
of the users.

I am assigning a fixed address to each user using a configuration like:

class "myClass" { match if (substring ((option agent.circuit-id),4,2) =
09:02); }

subnet netmask {
	option routers;
	pool { allow members of "myClass"; range; }

But this writes a lease binding users actual mac address to the ip
address So if the user changes hardware I get a "no free
leases" error in the logfiles and nothing works until the lease expires.

Setting the lease time very low is not an option since I have a ton of
users on the dhcp server and it kills the cpu and network. Yes... I have
tried :)

Other option is creating a script that watches the logfile and
automatically edits the lease files when the log error occurs. But that
requires a dhcpd restart, which is not sexy.

Any way to force the dhcp server to automatically overwrite leases in
this kind of setup?

Thanks for any help...


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