Thanks to all, I appreciate your help!
I have a 4006 CatOS switch running 6.3, I can telnet and authenticate via TACACS servers, how do I make sure I'm able to serial console to the switch in the event IP connectivity to the TACACS servers is lost or the TACACS servers are down? This the AAA config:
#authentication
set authentication login tacacs enable telnet primary
set authentication login tacacs enable http primary
set authentication enable tacacs enable telnet primary
set authentication enable tacacs enable http primary
set authentication login attempt 5 console
!
#authorization
set authorization exec enable tacacs+ deny console
set authorization exec enable tacacs+ deny telnet
set authorization enable enable tacacs+ deny console
set authorization enable enable tacacs+ deny telnet
set authorization commands enable all tacacs+ deny console
set authorization commands enable all tacacs+ deny telnet
end