The Cisco IOS’s AAA architecture contains many handy features, including authorizing and logging every CLI command executed on the router. Unfortunately, the AAA command accounting only supports TACACS+ as the AAA transport protocol, making it unusable in RADIUS environments.
You can use Embedded Event Manager as a workaround. The following configuration commands will log every command executed on the router.
Note: IOS implements standard syslog stream over TCP, not the more complex RFC 3195.
To support syslog over TCP, you also need TCP-capable syslog server. In Unix environments, you can use syslog-ng, on Windows, Kiwi syslog daemon is a perfect choice.
Note: to enable syslog over TCP in Kiwi Syslog Daemon, go to File/Setup/Inputs/TCP, click Listen for TCP Syslog messages and enter the desired TCP port number.
Very quietly, these logging events disappeared, first on 7500-series routers in IOS release 12.1(14), now they're gone by default on all platforms. If you still want to see what's going on with your frame-relay subinterfaces, you have to enter logging event subif-link-status configuration command on every subinterface.
I can only guess that some people that used the syslog events for network management were very surprised by the first (undetected) frame-relay failure following an IOS upgrade :)