The radius-disconnect trigger allows not to immediately terminate the user’s session upon receiving a request from the radius server to terminate the session, but to wait until the client requests an extension of the IP address lease and only then send FORCERENEW to the client and terminate the session.
It is useful when the client’s IP address has been changed, for example, and if the session is terminated, he will be left without the Internet until the next request to extend the IP address, but the session will be active until he requests an extension of the IP.
I will note that such behavior is unpredictable, for example, very rarely, but still there are problematic devices that may not request a new IP address when they receive FORCERENEW (see RFC3203 www.rfc-editor.org/rfc/rfc3203.html) or do not respond to DHCPNAK, or for example on some billings the session will remain active for a very long time, so I tested it and stopped using it.
It’s easy to set up:
edit system services dhcp-local-server
set reconfigure trigger radius-disconnect
There are more
edit access address-assignment pool 17217
set active-drain
request dhcp server reconfigure all
request dhcp server reconfigure 172.17.1.5
View information about clients:
run show subscribers
I also used a similar function once on accel-ppp, it was enabled by the soft-terminate=1 option in the ipoe section.
See also my article:
What is DHCP and how does it work?