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To view the spanning tree configuration and the interfaces that are participating in STP, use the show spanning-tree 0
command from EXEC privilege mode. If a physical interface is part of a port channel, only the port channel is listed in the
command output.
To confirm that a port is participating in Spanning Tree, use the show spanning-tree 0 brief command from EXEC
privilege mode.
DellEMC#show spanning-tree 0 brief
Executing IEEE compatible Spanning Tree Protocol
Root ID Priority 32768, Address 0001.e80d.2462
We are the root of the spanning tree
Root Bridge hello time 2, max age 20, forward delay 15
Bridge ID Priority 32768, Address 0001.e80d.2462
Configured hello time 2, max age 20, forward delay 15
Interface Designated
Name PortID Prio Cost Sts Cost Bridge ID PortID
-------------- ------ ---- ---- --- ----- --------------------
Te 1/1 8.496 8 4 DIS 0 32768 0001.e80d.2462 8.496
Te 1/2 8.497 8 4 DIS 0 32768 0001.e80d.2462 8.497
Te 1/3 8.513 8 4 FWD 0 32768 0001.e80d.2462 8.513
Te 1/4 8.514 8 4 FWD 0 32768 0001.e80d.2462 8.514
DellEMC#
Adding an Interface to the Spanning Tree Group
To add a Layer 2 interface to the spanning tree topology, use the following command.
● Enable spanning tree on a Layer 2 interface.
INTERFACE mode
spanning-tree 0
Modifying Global Parameters
You can modify the spanning tree parameters. The root bridge sets the values for forward-delay, hello-time, and max-age and
overwrites the values set on other bridges participating in STP.
NOTE:
Dell EMC Networking recommends that only experienced network administrators change the spanning tree
parameters. Poorly planned modification of the spanning tree parameters can negatively affect network performance.
The following table displays the default values for STP.
Table 113. STP Default Values
STP Parameters Default Value
Forward Delay 15 seconds
Hello Time 2 seconds
Max Age 20 seconds
Port Cost
● 100-Mb/s Ethernet interfaces
● 1-Gigabit Ethernet interfaces
● 10-Gigabit Ethernet interfaces
● 40-Gigabit Ethernet interfaces
● Port Channel with 100 Mb/s Ethernet interfaces
● Port Channel with 1-Gigabit Ethernet interfaces
● Port Channel with 10-Gigabit Ethernet interfaces
● Port Channel with 40-Gigabit Ethernet interfaces
● 200000
● 20000
● 2000
● 1400
● 180000
● 18000
● 1800
● 600
Port Priority 8
● Change the forward-delay parameter (the wait time before the interface enters the Forwarding state).
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Spanning Tree Protocol (STP)