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Configuring Multiple Spanning-Tree Protocol

You can configure the Multiple Spanning-Tree Protocol (MSTP) under the following hierarchy levels:

The routing instance type can be either virtual-switch or layer2-control.

To configure the Multiple Spanning-Tree Protocol:

  1. Enable RSTP as the version of spanning-tree protocol to be configured:
    [edit]
    user@host@ edit ... protocols mstp 
  2. (Optional) Enable provider bridge participation in the MSTP instance:
    [edit ... protocols mstp]
    user@host# set bpdu-destination-mac-address provider-bridge-group
  3. Configure the interfaces that participate in the MSTP instance.

    1. Enable configuration of the interface:
      [edit ... protocols mstp]
      user@host# edit interface interface-name
    2. Configure the interface priority:
      [edit ... protocols mstp interface interface-name]
      user@host# set priority interface-priority
    3. (Optional) By default, the interface link cost is determined by the link speed. You can configure the interface link cost to control which bridge is the designated bridge and which port is the designated port:
      [edit ... protocols mstp interface interface-name]
      user@host# set cost interface-link-cost
    4. Configure the interface link mode to identify point-to-point links:
      [edit ... protocols mstp interface interface-name]
      user@host# set mode (p2p | shared)

      Specify p2p if the link is point to point. Specify shared is the link is a shared media.

    5. (Optional) Configure the interface as an edge port:
      [edit ... protocols mstp interface interface-name]
      user@host# set edge

      Edge ports do not expect to receive bridge protocol data unit (BPDU) packets. If a BPDU packet is received for an edge port, the port becomes a nonedge port

    You can also enable BPDU root protection for all spanning-tree protocol instances on the interface. BPDU root protect ensures the port is the spanning-tree designated port. If the port receives superior BPDU packets, root protect moves this port to a root-prevented spanning-tree state. For configuration details, see Checking the Status of Spanning-Tree Instance Interfaces.
  4. Configure the bridge priority
    [edit ... protocols mstp]
    user@host# set bridge-priority bridge-priority

    For more information, see Bridge Priority for Election of Root Bridge and Designated Bridge.

  5. Configure hello BPDU timers.

    1. Configure the maximum expected arrival time of hello BPDUs:
      [edit ... protocols mstp]
      user@host# set max-age seconds
    2. Configure the time interval at which the root bridge transmits configuration BPDUs:
      [edit ... protocols mstp]
      user@host# set hello-time seconds
  6. (Optional) By default, the bridge port remains in the listening and learning states for 15 seconds before transitioning to the forwarding state. You can specify a delay from 4 through 20 seconds instead:
    [edit ... protocols mstp]
    user@host# set forward-delay seconds
  7. Configure MSTP-specific options.

    1. Configure the MSTP region configuration name:
      [edit ... protocols mstp]
      user@host# set configuration-name configuration-name
    2. Configure the MSTP revision level:
      [edit ... protocols mstp]
      user@host# set revision-levelrevision-level revision-level
    3. Configure the maximum number of hops a BPDU can be forwarded in the MSTP region:
      [edit ... protocols mstp]
      user@host# set max-hops hops
  8. Verify the MSTP configuration:

    [edit]... { # Optional logical system and/or routing instanceprotocols {mstp {bpdu-destination-mac-address provider-bridge-group; # Optionalinterface interface-name {priority interface-priority;cost interface-link-cost; # Optional.mode (p2p | shared);edge; # Optional.}bridge-priority bridge-priority;max-age seconds;hello-time seconds;forward-delay seconds; # Optional.configuration-name configuration-name; # MST region configuration name.revision-level revision-level; # MST revision number.max-hops hops; # MST maximum hops.}}}

Published: 2011-11-01