Tags:access-switch bpdu catalyst-switch Cisco portfast spanning-tree stp switching-loop
STP Portfast is a feature in Cisco IOS which allows a switchport which is participating in STP to directly transition from Blocking mode to Forwarding mode when a device connects and the link goes up. This can improve the initial connect time and can fix some issues with Windows based devices connecting to the Active Directory domains.
STP Portfast is ideal for ports which connects directly attached devices and certainly not for the ports which connects a hub or a switch. Hence, good to set switchports that directly connect end devices on your Access switch.
To enable STP Portfast in Cisco Catalyst switches running Cisco IOS
Enter Interface Configuration Mode
ciscoswitch# conf term
ciscoswitch(config)# int gigabitethernet 1/10
ciscoswitch(config-if)# no shut
NOTE: If the port was initially shutdown
Force the switchport mode to Access
ciscoswitch(config-if)# switchport mode access
ciscoswitch(config-if)# spanning-tree 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 GigabitEthernet1/10 but will only have effect when the interface is in a non-trunking mode.
Enable BPDU Guard
BPDU guard protects against a switching loop. On a switchport with BPDU Guard, when a BPDU arrives, the port will be shut down and placed into error disabled (err-disabled) state. This port needs to be enabled manually later on.
ciscoswitch(config-if)# spanning-tree bpduguard enable
This should enabled Spanning tree portfast in a Cisco Catalyst switch running Cisco IOS.