IBM 12.1(22)EA6 - Manual (Page 214)

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Cisco Systems Intelligent Gigabit Ethernet Switch Modules for the IBM BladeCenter, Software Configuration Guide
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Chapter 11 Configuring Optional Spanning-Tree Features
Understanding Optional Spanning-Tree Features
Understanding Port Fast
Port Fast immediately brings an interface configured as an access or trunk port from a blocking state to
the forwarding state, bypassing the listening and learning states. You can use Port Fast on ports
connected to a single workstation or server, as shown in
Figure 11-1 , to allow those devices to
immediately connect to the network, rather than waiting for the spanning tree to converge.
Ports connected to a single workstation or server should not receive bridge protocol data units (BPDUs).
A port with Port Fast enabled goes through the normal cycle of spanning-tree status changes when the
switch is restarted.
Note Because the purpose of Port Fast is to minimize the time ports must wait for spanning-tree to converge,
it is effective only when used on ports connected to end stations. If you enable Port Fast on a port
connected 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.
Figure 11-1 Port Fast-Enabled Ports
Catalyst 6000
series switch
Catalyst 3550
switch
Workstations BladeCenter
Catalyst 2950, 2955,
or 3550 switch
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