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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:

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

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

  1. Enable configuration of a MST instance:

    [edit]
    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) 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 msti msti-id interface interface-name]
      user@host# set cost interface-link-cost
    4. (Optional) Configure the interface as an edge port:

      [edit ... protocols mstp msti msti-id 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

  3. Configure the bridge priority

    [edit ... protocols mstp msti msti-id]
    user@host# set bridge-priority bridge-priority

    For more information, see 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:

    [edit]
    user@host# set vlan (vlan-id | vlan-id-range)
  5. Verify the MST interface configuration.

    [edit]protocols {mstp {...basic-mstp-configuration...msti msti-id { # Instance identifier 1 – 64.bridge-priority priority; vlan vlan-id; # Optionalinterface interface-name {cost cost;edge;priority interface-priority;}}}}

Published: 2010-05-11

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