If you have a server or other devices connected into your switch that you’re totally sure won’t
create a switching loop if STP is disabled, you can use something called PortFast on these
ports. Using it means the port won’t spend the usual 50 seconds to come up into forwarding
mode while STP is converging.
Switch(config-if)#spanning-tree portfast ?
disable Disable portfast for this interface
trunk Enable portfast on the interface even in trunk mode
Let’s take a look at the message I get when I turn PortFast on an interface:
Switch(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 FastEthernet0/1 but will only
have effect when the interface is in a non-trunking mode.
Switch(config-if)#