This reports the IP address of the TACACS+ server that the device most recently contacted for an authentication, authorization, or accounting request. An admin checks this to confirm which server in a multi-server TACACS+ deployment actually handled the last request, useful for diagnosing whether traffic is reaching the intended primary server or has failed over to a backup. For example, if an admin expected requests to go to a primary server at 10.1.1.1 but rcTacacsGlobalLastAddress shows a backup server's address instead, that would indicate the primary server is unreachable and requests are failing over.