"show post"
This command will show you the results of the POST when the switch was turned on.
!!NOTE!!
I don't think this command works on all Cisco switches, but I don't have a list for you. The example output is from a 2960S switch.
*****EXAMPLE OUTPUT*****
Switch 2
---------
POST: MA BIST : Begin
FC 1 MBIST Test Passed.
DP Sg1 MBIST Test Passed.
DP Xg1 MBIST Test Passed.
NI 1 MBIST Test Passed.
FC 0 MBIST Test Passed.
DP Sg0 MBIST Test Passed.
DP Xg0 MBIST Test Passed.
NI 0 MBIST Test Passed.
UPB MBIST Test Passed.
POST: MA BIST : End, Status Passed
POST: TCAM BIST : Begin
POST: TCAM BIST : End, Status Passed
POST: Inline Power Controller Tests : Begin
POST: Inline Power Controller Tests : End, Status Passed
POST: Thermal, Fan Tests : Begin
POST: Thermal, Fan Tests : End, Status Passed
POST: PortASIC Stack Port Loopback Tests : Begin
POST: PortASIC Stack Port Loopback Tests : End, Status Passed
POST: PortASIC Port Loopback Tests : Begin
POST: PortASIC Port Loopback Tests : End, Status Passed
POST: EMAC Loopback Tests : Begin
POST: EMAC Loopback Tests : End, Status Passed