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8-9
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide
—
Release 8.1
78-15486-01
Chapter 8 Configuring Spanning Tree PortFast, BPDU Guard, BPDU Filter, UplinkFast, BackboneFast, and Loop Guard
Configuring PortFast
This example shows how to enable PortFast on port 1 of module 4 and verify the configuration (the
PortFast status is shown in the “Fast-Start” column):
Console> (enable) set spantree portfast 4/1 enable
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 Priority Fast-Start Group-method
--------- ---- ------------- ----- -------- ---------- ------------
4/1 1 blocking 19 20 enabled
4/1 100 forwarding 10 20 enabled
4/1 521 blocking 19 20 enabled
4/1 522 blocking 19 20 enabled
4/1 523 blocking 19 20 enabled
4/1 524 blocking 19 20 enabled
4/1 1003 not-connected 19 20 enabled
4/1 1005 not-connected 19 4 enabled
Console> (enable)
Enabling PortFast on a Trunk Port
Caution
You can use PortFast to connect a single end station or a switch port to a switch port. If you enable
PortFast on a port that is connected to another Layer 2 device, like a switch, you might create network
loops.
To enable PortFast on a trunk port, perform this task in privileged mode:
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
Task
Command
Step 1
Enable PortFast on a trunk port that is
connected to a single workstation, switch,
or server.
set spantree portfast mod_num/port_num enable trunk
Note
If you enter the set spantree portfast command
on a trunk port without entering the trunk
keyword, the trunk port stays in disable mode.
Step 2
Verify the PortFast setting on a trunk port.
show spantree portfast [mod_num/port_num]