host-identifier and option 82

[Marc Perea]

Greetings,
I'm chiming in here because we (an ISP) had a similar situation and use case and I hope to head off a possible gotcha' if I can. It sounds to me like you want the dhcpd service to hand back a specific IP per option 82 circuit, regardless of which MAC address is presented. Is that accurate?
Even though using the static host entry with option 82 does not result in a MAC address being written to a file, I don't believe that means that you can swap a new MAC in and have it "just work". In my estimation, the primary key of the in RAM leasing structure is still the MAC address - or at least the results I've seen first hand seem to indicate this. We have a few methods of "clearing the lease" - which although static is still necessary for a new MAC to obtain service. Even though you short circuit and bypass the leases file by using static assignment, the dhcp server is still making a promise to some end device that the IP x.y.z.a is available for it's _exclusive_ use for the next lease_time seconds. That still gets tracked, and I believe it's tracked by MAC. So, if you plug another device into the same circuit as one that has an existing lease, you will find yourself with the no available leases error in your logs. At least we do.
 
One way to fix would be to look for that error and auto-clear leases as others have described. We've implemented a button on our support webpage that does the same, as well as a the ability for a tech. to text (SMS) a special number and have our systems perform the clear. By the way, using OMAPI you don't have to actually set the state of the lease to free - it is enough to just modify the ends time. We set the ends to 0, update, and the lease is free and available.

Regards,
--Marc
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