Follow these steps to configure and enable MSTP on an Ethernet interface.
The parameters can be configured individually on an interface by:
- Entering the commands in Steps 1 through Step 3 for the target interface
- Running the relevant parameter command
- Verifying the result
- Saving the configuration
For detailed descriptions of the parameters and features, see the sections STP parameters and STP features.
-
Enter configuration mode.
device# configure terminal
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Enable MSTP.
device(config)# protocol spanning-tree mstp
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Enter interface configuration mode.
device(config-mstp)# interface ethernet 0/5
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Enable the interface.
device(conf-if-eth-0/5)# no shutdown
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Configure the restricted role feature for the port.
device(conf-if-eth-0/5)# spanning-tree restricted-role
This command keeps a port from becoming a root.
-
Restrict topology change notifications (TCN) BPDUs for an MSTP instance.
device(conf-if-eth-0/5)# spanning-tree instance 5 restricted-tcn
This prevents the port from propagating received TCNs and topology changes originating from a bridge, external to the core network, to other ports.
-
Enable auto detection of an MSTP edge port.
device(conf-if-eth-0/5)# spanning-tree autoedge
Enabling this feature allows the system to automatically identify the edge port. The port can become an edge port if no BPDU is received. By default, automatic edge detection is disabled.
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device(conf-if-eth-0/5)# spanning-tree edgeport
Enabling edge port allows the port to quickly transition to the forwarding state. By default, automatic edge detection is disabled.
-
Enable BPDU guard on the port
device(conf-if-eth-0/5)# spanning-tree edgeport bpdu-guard
BPDU guard removes a node that reflects BPDUs back in the network. It enforces the STP domain borders and keeps the active topology predictable by not allowing any network devices behind a BPDU guard-enabled port to participate in STP.
-
Set the path cost of a port.
device(conf-if-eth-0/5)# spanning-tree cost 200000
The path cost range is from 1 to 200000000. Leaving the default adjusts path cost relative to changes in the bandwidth. A lower path cost indicates greater likelihood of becoming root port.
-
Configure the link type.
device(conf-if-eth-0/5)# spanning-tree link-type point-to-point
The options are
point-to-point or
shared.
-
Enable port priority.
device(conf-if-eth-0/5)# spanning-tree priority 128
The range is from 0 to 240 in increments of 16 with a default of 32. A lower priority indicates greater likelihood of becoming root port.
-
Return to privileged exec mode.
device(conf-if-eth-0/5)# end
-
Verify the configuration.
device# show spanning-tree interface ethernet 0/5
Spanning-tree Mode: Multiple Spanning Tree Protocol
Root Id: 8000.001b.ed9f.1700
Bridge Id: 8000.01e0.5200.011d
Port Eth 0/5 enabled
Ifindex: 411271175; Id: 8002; Role: Designated; State: Forwarding
Designated External Path Cost: 0; Internal Path Cost: 20000000
Configured Path Cost: 200000
Designated Port Id: 8002; Port Priority: 128
Designated Bridge: 8000.01e0.5200.011d
Number of forward-transitions: 1
Version: Multiple Spanning Tree Protocol - Received MSTP - Sent MSTP
Edgeport: yes; AutoEdge: yes; AdminEdge: no; EdgeDelay: 3 sec
Restricted-role is enabled
Restricted-tcn is enabled
Boundary: no
Bpdu-guard: on
Link-type: point-to-point
Received BPDUs: 86; Sent BPDUs: 1654
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Save the configuration.
device# copy running-config startup-config
