Logging virtual server state event up or down

I'm having a bit of curiosity, i can see a log at /var/log/ltm when a pool or pool member up/down.

May 22 14:46:53 slot1/lb01 notice mcpd[5902]: 01070638:5: Pool xxxxxxxx member /Common/10.2.203.130:5057 monitor status down. [ was up for 0hr:1min:15sec ]

But i cannot find any log when a Virtual server state is up or down. Is it just me or there isn't any event like that? or is there any way to create the event?

Thanks

Fadhil