2.1.f Implement and troubleshoot spanning-tree

once in a while it’s refreshing to go back… turn on debug spanning-tree… be sure to set the service timestamps debug datetime in global configuration mode…

als1(config-if)#
*Mar 13 13:36:25: set portid: VLAN0001 Fa0/6: new port id 8006
*Mar 13 13:36:25: STP: VLAN0001 Fa0/6 -> listening
als1(config-if)#
*Mar 13 13:36:26: %LINK-3-UPDOWN: Interface FastEthernet0/6, changed state to up
*Mar 13 13:36:27: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0p
als1(config-if)#
*Mar 13 13:36:40: STP: VLAN0001 Fa0/6 -> learning
als1(config-if)#
*Mar 13 13:36:55: STP: VLAN0001 sent Topology Change Notice on Fa0/7
*Mar 13 13:36:55: STP: VLAN0001 Fa0/6 -> forwarding
als1(config-if)#shut
als1(config-if)#
*Mar 13 13:37:51: STP: VLAN0001 sent Topology Change Notice on Fa0/7
als1(config-if)#
*Mar 13 13:37:53: %LINK-5-CHANGED: Interface FastEthernet0/6, changed state to n
*Mar 13 13:37:54: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0n
als1(config-if)#spann portfast 
%Warning: portfast should only be enabled on ports connected to a single
host. Connecting hubs, concentrators, switches, bridges, etc… to this
interface  when portfast is enabled, can cause temporary bridging loops.
Use with CAUTION

%Portfast has been configured on FastEthernet0/6 but will only
have effect when the interface is in a non-trunking mode.
als1(config-if)#no shut
als1(config-if)#
*Mar 13 13:38:12: set portid: VLAN0001 Fa0/6: new port id 8006
*Mar 13 13:38:12: STP: VLAN0001 Fa0/6 ->jump to forwarding from blocking  

like a favorite old flannel shirt…