looking for help on an unusual config

dan dandenson at gmail.com
Wed Sep 21 20:45:13 UTC 2022

Hi all.  I'm looking for some help to make a rather unusual config for a
radius backed DHCP server

I want the DHCP server to hand out addresses based on an 'id' that is in a
descending list of fields in the DHCP request.  This is using DHCP Option
82 to add in Agent remote id and circuit id.

so, remote id, then circuit id, then mac address in that order.  If there's
no remote id, then use circuit id and so on.

The goal here is that whatever device/port a user connects THROUGH will add
the remote or circuit ID to the request and then the DHCP server will setup
a dynamic lease matching that data.  MAC address is a 'backup' basically.
Then that address is in there with a very long lease, say 1 year.  If the
user swaps out their own device (home wifi router...) then it will request
DHCP *through* the intermediate device (a switch or bridge interface on
another device) it will get handed the same IP from that lease that's based
on the option 82 info.  ie, customer/user gets a consistent IP address even
when swapping their device out.

It appears that all DHCP servers work under the assumption that if you want
to do something like this you'll radius back it against a database w/ CRM
etc.  I don't really care about the database part of this initially.

Thoughts?  is this something freeradius can be configured to handle without
adding a database backend?


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