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Chapter 4
Layer 2 Switching and the Spanning Tree Protocol (STP)
1900A(config)#no spantree 1
1900A#sh span 1
Error: STP is not enabled for VLAN 1
1900A#config t
Enter configuration commands, one per line. End with
CNTL/Z
1900A(config)#span 1
1900A#sh span 1
VLAN1 is executing the IEEE compatible Spanning Tree
Protocol
Bridge Identifier has priority 32768, address
0030.80CC.7B40
Configured hello time 2, max age 20, forward delay 15
Current root has priority 32768, address 0030.80CC.7B40
Root port is N/A, cost of root path is 0
Topology change flag not set, detected flag not set
Topology changes 0, last topology change occurred
0d00h00m00s ago
Times: hold 1, topology change 8960
hello 2, max age 20, forward delay 15
Timers: hello 2, topology change 35, notification 2
Port Ethernet 0/1 of VLAN1 is Forwarding
[output cut]
Notice in the above output that the no spantree 1 command turned off
spanning tree for VLAN 1. Typing spantree 1 (span 1 for short) turned the
Spanning Tree Protocol back on for VLAN 1. The show spantree 1 com-
mand displays the STP information for VLAN 1. Notice that the bridge ID,
MAC address, and timers are displayed.
To see the spanning tree configuration and whether it is active on a
Catalyst 5000 set-based switch, use the show spantree command as
shown here:
Todd5000> (enable) show spantree
VLAN 1
Spanning tree enabled
Spanning tree type ieee
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