Understanding Optional Spanning-Tree Features; Understanding Port Fast; Configuring Optional Spanning-Tree Features - Cisco Catalyst 3750 Software Configuration Manual

Understanding Optional Spanning-Tree Features

Understanding 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, as shown in
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
Note
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.
If your switch is running PVST+, rapid PVST+, or MSTP, you can enable this feature by using the
spanning-tree portfast interface configuration or the spanning-tree portfast default global
configuration command.
Figure 16-1 Port Fast-Enabled Interfaces
Workstations
Catalyst 3750 Metro Switch Software Configuration Guide
16-2
Port
Fast-enabled
ports
Workstations
Chapter 16

Configuring Optional Spanning-Tree Features

Figure 16-1, to allow those devices to
Server
Port
Fast-enabled port
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