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    Configuring MST Instances on a Physical Interface

    You can configure a Multiple Spanning-Tree Instance (MSTI) under the following hierarchy levels:

    Before you begin, configure Multiple Spanning-Tree Protocol. For configuration details, see Configuring MSTP.

    1. Enable configuration of a MST instance:
      user@host# edit ... protocols mstp msti msti-id

      The msti-id value must be from 1 through 64.

    2. Configure the interfaces that participate in the MST instance.

      1. Enable configuration of the interface:
        [edit ... protocols mstp msti msti-id]
        user@host# edit interface interface-name
      2. Configure the interface priority:
        [edit ... protocols mstp msti msti-id interface interface-name]
        user@host# set priority interface-priority
      3. (Optional) Configure the interface as an edge port:
        [edit ... protocols mstp msti msti-id interface interface-name]
        user@host# set edge
    3. Configure the bridge priority
      [edit ... protocols mstp msti msti-id]
      user@host# set bridge-priority bridge-priority

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

    4. (Optional) An MSTI can map to a range of VLANs just as a logical port can map to a range of VLANs. The MSTP VLAN specifies the VLAN or VLAN range to which this MSTI is mapped. The vlan-id is configured under the logical interface. Configure the VLAN or VLAN range of the MSTI instance:
      user@host# set vlan (vlan-id | vlan-id-range)
    5. Verify the MST interface configuration.

      msti msti-id { # Instance identifier 1 – 64.
      bridge-priority priority;
      vlan vlan-id; # Optional
      interface interface-name {
      cost cost;
      priority interface-priority;

    Note: All STP ports on a bridge domain must belong to the same MST (multiple spanning tree) instance.

    Modified: 2018-03-08