User's Manual

Table Of Contents
241
Users Manual of CS-6306R
Chapter 20. STP Optional Characteristic
Configuration
Configuring STP Optional Characteristic 20.1
20.1.1 STP Optional Characteristic Introduction
The spanning tree protocol module of the switch supports seven additional features (the so-called optional
features). These features are not configured by default. The supported condition of various spanning tree
protocol modes towards the optional characteristics is as follows:
Optional Characteristic Single STP PVST RSTP MSTP
Port Fast Yes Yes No No
BPDU Guard Yes Yes Yes Yes
BPDU Filter Yes Yes No No
Uplink Fast Yes Yes No No
Backbone Fast Yes Yes No No
Root Guard Yes Yes Yes Yes
Loop Guard Yes Yes Yes Yes
20.1.1.1 Port Fast
Port Fast immediately brings an interface configured as an access or trunk port to the forwarding state from a
blocking state, bypassing the listening and learning states. You can use Port Fast on interfaces connected to
a single workstation or server, to allow those devices to immediately connect to the network, rather than
waiting for the spanning tree to converge.
Interfaces connected to a single workstation or server should not receive bridge protocol data units (BPDUs).
An interface with Port Fast enabled goes through the normal cycle of spanning-tree status changes when the
switch is restarted.
Because the purpose of Port Fast is to minimize the time interfaces must wait for spanning-tree to converge, it
is effective only when used on interfaces connected to end stations. If you enable Port Fast on an interface
connecting to another switch, you risk creating a spanning-tree loop.
You can enable this feature by using the spanning-tree portfast interface configuration or the spanning-tree
portfast default global configuration command.