Cisco IE-4000 Software Configuration Manual page 357

Configuring Optional Spanning-Tree
Features
Prerequisites for the Optional Spanning-Tree Features
You can configure all of these features when your switch is running the per-VLAN spanning-tree plus (PVST+). You can
configure only the noted features when your switch is running the Multiple Spanning Tree Protocol (MSTP) or the rapid
per-VLAN spanning-tree plus (rapid-PVST+) protocol.
Restrictions for the Optional Spanning-Tree Features
You can configure the UplinkFast or the BackboneFast feature for rapid PVST+ or for the MSTP, but the feature remains
disabled (inactive) until you change the spanning-tree mode to PVST+.
Information About Configuring the Optional Spanning-Tree
Features
PortFast
PortFast 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 PortFast on interfaces connected to a single workstation
or server, as shown in
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 PortFast enabled goes through the normal cycle of spanning-tree status changes when the switch is restarted.
Note: Because the purpose of PortFast 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 PortFast 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.
Figure 44 on page 354, to allow those devices to immediately connect to the network, rather than
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