Automatic remove lease from pool

Lars Jacobsen lars-jacobsen at
Wed May 23 20:43:09 UTC 2007

>Henrik Sterndorff Jessen wrote:
> 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.

That seams to be the idea of DHCP/rfc ;-)
How can you be shure that the user dont change back to the "original" 
hardware again ?
Explain to your users that they have leased the IP for X minuttes and if 
they can not figure out how to manually release the IP if/when they change 
their hardware, they have to wait Y minutes before things start working 

> 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 :)

Hmmm, performance problems usually is because to "small" hardware or poor 
There are people on the list with 30-50.000 users/clients on ISC, so I dont 
think the server app. is the killer.
Hopefully you dont have a ton of "users" on the server, but a lots of client 
requests. If you are not running on a dedikated server then take a look at 
what processes is killing your server.

> 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?

Maybe another hack to the server so that it binds the lease to the opt. 82 
CID instead of client ID/hardware/mac. Know this is agaist rfc but if thats 
what you want. Of cource you have to make absolute certain that the opt. 82 
CID is unique all over the network - usually thats no big problem for ISP 
like you ;-)

> Thanks for any help...
> Regards,
> /Henrik


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