Subscriber Services: Limit subscriber sessions per user & access profile

Support for configuring a limit on the number of sessions that can be active for a given username in an access profile with the session-limit-per-username statement. The show network-access aaa statistics session-limit-per-username command displays the number of active sessions and the number of blocked requests for usernames in each access profile. The clear network-access aaa statistics session-limit-per-username command clears blocked requests for debugging subscriber session limits.