User Guide 398
Configuring Spanning Tree STP/RSTP Configurations
Step 4 spanning-tree common-config [ port-priority
pri
] [ ext-cost
ext-cost
] [ portfast { enable |
disable }] [ point-to-point { auto | open | close }]
Configure STP/RSTP parameters on the desired port .
pri:
Specify the Priority for the desired port. The value should be an integral multiple of 16,
ranging from 0 to 240. The default value is 128. Ports with lower values have higher priority.
When the root path of the port is the same as other ports’, the switch will compare the port
priorities and select a root port with the highest priority.
ext-cost:
Specify the value of the external path cost. The valid values are from 0 to 2000000
and the default setting is Auto, which means the port calculates the external path cost
automatically according to the port’s link speed.
For STP/RSTP, external path cost indicates the path cost of the port in spanning tree. The Port
with the lowest root path cost will be elected as the root port of the switch.
For MSTP, external path cost indicates the path cost of the port in CST.
portfast { enable | disable }: Enable to set the port as an edge port. By default, it is disabled.
When the topology is changed, the edge port can transit its state from blocking to forwarding
directly. For the quick generation of the spanning tree, it is recommended to set the ports that
are connected to the end devices as edge ports.
point-to-point { auto | open | close }:
Select the status of the P2P (Point-to-Point) link to which
the ports are connected. During the regeneration of the spanning tree, if the port of P2P link
is elected as the root port or the designated port, it can transit its state to forwarding directly.
Auto indicates that the switch automatically checks if the port is connected to a P2P link, then
sets the status as Open or Closed. Open is used to set the port as the one that is connected to
a P2P link. Close is used to set the port as the one that is not connected to a P2P link.
Step 5 spanning-tree mcheck
(Optional) Perform MCheck operations on the port.
If a port on an RSTP-enabled/MSTP-enabled device is connected to an STP-enabled device,
the port will switch to STP compatible mode and send packets in STP format. MCheck is
used to switch the mode of the port back to RSTP/MSTP after the port is disconnected from
the STP-enabled device. The MCheck configuration can take effect only once, after that the
MCheck status of the port will switch to Disabled.
Step 6 show spanning-tree interface [ fastEthernet
port
| gigabitEthernet
port
| ten-
gigabitEthernet
port
| port-channel
lagid
] [ edge | ext-cost | int-cost | mode | p2p | priority |
role | state | status ]
(Optional) View the information of all ports or a specified port.
port:
Specify the port number.
lagid:
Specify the ID of the LAG.
ext-cost | int-cost | mode | p2p | priority | role | state | status: Display the specified information.
Step 7 end
Return to privileged EXEC mode.
Step 8 copy running-config startup-config
Save the settings in the configuration file.
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