To guarantee that an account session ID is unique across router reboots, we added the following config to our LNS routers:
routert#conf t
router(config)#radius-server unique-ident 1
router(config)#end
router#wr m
If we ever replace a router, we need to increment the unique-ident number to ensure that the new router does not re-use the same session-id's as the old one. This is because we use nas:sessionid as the unique key to identify a session.
We had problems with this not working on our Cisco 7200 routers running 12.3(26), but expect that we need to upgrade to 12.3(2)T or 12.4 as per Cisco's documentation.
Reference: http://www.cisco.com/en/US/docs/ios/12_3t/12_3t2/feature/guide/ftradaid…