Assigning IP addresses based on Option 82 information

Dave Brodin dbrodin at
Thu Jun 21 14:30:36 UTC 2007

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

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

Any help would be greatly appreciated.

Dave Brodin
Network Operations
Smithville Digital

More information about the dhcp-users mailing list