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Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 9 Configuring Spanning-Tree PortFast, UplinkFast, BackboneFast, and Loop Guard
Configuring PortFast on the Switch
This example shows how to enable PortFast on port 1 of module 4 of a trunk port, bring the trunk port
to a forwarding state, and verify the configuration (the PortFast status is shown in the “Fast-Start”
column):
Console> (enable) set spantree portfast 4/1 enable trunk
Warning:Connecting Layer 2 devices to a fast start port can cause
temporary spanning tree loops. Use with caution.
Spantree port 4/1 fast start enabled.
Console> (enable) show spantree 4/1
Port Vlan Port-State Cost Prio Portfast
Channel_id
------------------------ ---- ------------- --------- ---- ------------------
4/1 1 blocking 4 32 enabled 0
4/1 100 forwarding 4 32 enabled 0
4/1 521 blocking 4 32 enabled 0
4/1 524 blocking 4 32 enabled 0
4/1 1003 not-connected 4 32 enabled 0
4/1 1005 not-connected 4 32 enabled 0
Console> (enable) show spantree portfast 4/1
Portfast:enable trunk
Portfast BPDU guard is disabled.
Portfast BPDU filter is disabled.
Console>
Note When PortFast is enabled between two switches, the system will verify that there are no loops in the
network before bringing the blocking trunk to a forwarding state.
Disabling PortFast
To disable PortFast on a switch or trunk port, perform this task in privileged mode:
This example shows how to disable PortFast on port 1 of module 4:
Console> (enable) set spantree portfast 4/1 disable
Spantree port 4/1 fast start disabled.
Console> (enable)
Task Command
Step 1
Disable PortFast on a switch port. set spantree portfast mod_num/port_num
disable
Step 2
Verify the PortFast setting. show spantree mod_num/port_num
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