Cisco Systems OL-8241-02 Manual De Usuario

By default, an Ethernet interface is set to the enabled bridge state. Use the bridge 
state command to set the spanning-tree bridge state for an Ethernet interface or 
for a trunked Ethernet interface. 

For example, to enable the bridge state for e7 on the CSS 11501, enter:

(config-if[e7])# bridge state enable

For example, to enable the bridge state for the I/O module in slot 1, Ethernet 
port 1, in VLAN3, enter:

(config-if-vlan[1/1-3])# bridge state enable

To disable the bridge state, enter:

(config-if-vlan[1/1-3])# bridge state disable

The Port Fast feature immediately brings a CSS Ethernet interface (port) to the 
Spanning Tree Protocol (STP) forwarding state from a blocking state, bypassing 
the listening and learning states. You can specify Port Fast for ports connected to 
a single workstation or server to allow those devices to immediately connect to 
the network, rather than waiting for the STP to converge. 

Ports connected to a single workstation or server should not receive bridge 
protocol data units (BPDUs). 

The purpose of Port Fast is to minimize the time ports must wait for STP to 
converge. This means that the Port Fast function is effective only when used on 
ports connected to end stations in the network. If you enable Port Fast on a port 
connecting to another switch, you risk creating a spanning-tree loop. Consider 
using the BDPU guard feature to avoid creating a spanning-tree loop.

This section includes the following topics: