Configuring PortFast

Configuring PortFast
To configure PortFast on a switch, use the set spantree portfast command. The following
switch output shows how to configure ports 2/1–12 with PortFast:
Terry_4000> (enable) set spantree portfast ?
Usage: set spantree portfast <mod_num/port_num> <enable|disable>
set spantree portfast <trcrf> <enable|disable>
Terry_4000> (enable) set spantree portfast 2/1-12 enable
Warning: Spantree port fast start should only be enabled on ports connected
to a single host. Connecting hubs, concentrators, switches, bridges, etc. to a
fast start port can cause temporary spanning tree loops. Use with caution.
Spantree ports 2/1-12 fast start enabled.
Terry_4000> (enable)
Notice the nice warning received on the switch console when PortFast was turned on. Also
notice that we were able to turn on all 12 ports of our 10/100 card.
To configure PortFast on an IOS-based switch, use the spanning-tree portfast interface
command:
Terry_2950(config)#int fa 0/12
Terry_2950(config-if)#switchport mode access
Terry_2950(config-if)#spanning-tree ?
bpdufilter Don't send or receive BPDUs on this interface
bpduguard Don't accept BPDUs on this interface
cost Change an interface's spanning tree port path cost
guard Change an interface's spanning tree guard mode
link-type Specify a link type for spanning tree protocol use
port-priority Change an interface's spanning tree port priority
portfast Enable an interface to move directly to forwarding on link up
stack-port Enable stack port
vlan VLAN Switch Spanning Tree
Terry_2950(config-if)#spanning-tree port
Terry_2950(config-if)#spanning-tree portfast ?
disable Disable portfast for this interface
trunk Enable portfast on the interface even in trunk mode
<cr>
Terry_2950(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 FastEthernet0/12 but will only have effect
when the interface is in a non-trunking mode.
Terry_2950(config-if)
This parameter must be configured on each port you want to run PortFast. Note the words
of caution associated with this command.