Assigning IP addresses based on Option 82 information

Lars Jacobsen lars-jacobsen at
Thu Jun 21 19:28:30 UTC 2007

> "Dave Brodin" wrote:
Subject: Assigning IP addresses based on Option 82 information

> With our old DHCP server (Cisco's Network Registrar), we were able to
> limit our DSL subscribers to one IP address based on their Option 82
> information (in our case ATM PVC).  I can do the same thing with ISC
> DHCP using classes:
> class "DHCP" {
>   spawn with pick(option agent.remote-id, remote-id);
>   if (exists agent.remote-id) {
>      set remote-id = option agent.remote-id;
>   }
>   if (exists agent.circuit-id) {
>      set circuit-id = option agent.circuit-id;
>   }
>   lease limit 1;
> }
> But the problem is that with Network Registrar, someone could change MAC
> addresses and still get the same IP address.  With ISC DHCP, they can't
> get another IP address until the old lease expires ("no available
> billing" in the logs).  This doesn't work well when the customer tries
> to swap out routers and most of them don't know how to do MAC spoofing
> to prevent the issue.
> From my web searches, it sounds like I may be out of luck as IP
> addresses are always tied to either the MAC address or the client
> identifier.
> I'm trying to avoid building anything more complicated like a web-based
> mac registration system, or trying to adapt something like NetReg to my
> needs.
> Any help would be greatly appreciated.
> --
> Dave Brodin
> Network Operations
> Smithville Digital

Yes, unfortunately its not posible yet to assign/bind IP´s to anything other 
that client ID or hardware/mac with ISC DHCPd, at the moment.
There has been several purposal that there should be an option to do so. I 
think ISC will incorporate such ting in a future release. Witch release and 
the timeframe is unown.
Until then only hacks like:
witch deals with a portion af the problem, seems to be the only alternative.
To my nowlege there has been no hacks that allows ISC DHCPd binding IP´s to 
ie. Option 82 Circut ID or Option 82 Remote ID, how convinent that might be 


More information about the dhcp-users mailing list