Technical Documentation

Configuring VLAN Spanning-Tree Protocol

You can configure the VLAN Spanning-Tree Protocol (VSTP) under the following hierarchy levels:

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

To configure the VLAN Spanning-Tree Protocol:

  1. Enable VSTP as the version of spanning-tree protocol to be configured:

    [edit]
    user@host@ edit ... protocols vstp
  2. (Optional) For compatibility with older bridges that do not support VSTP, you can run force VSTP to run as the original IEEE 802.1D Spanning-Tree Protocol (STP) version:

    [edit ... protocols vstp]user@host# set force-version stp

    Note: If VSTP has been forced to run as the original STP version, you can revert back to VSTP by first removing the force-version statement from the configuration and then entering the clear spanning-tree protocol-migration configuration mode command.

  3. Configure the interfaces that participate in the VSTP instance.

    1. Enable configuration of the interface:

      [edit ... protocols vstp]
      user@host# edit interface interface-name
    2. Configure the interface priority:

      [edit ... protocols vstp 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 vstp interface interface-name]
      user@host# set cost interface-link-cost
    4. Configure the interface link mode to identify point-to-point links:

      [edit ... protocols vstp 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 vstp 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. Enable configuration of a VLAN instance:

    [edit ... protocols vstp]
    user@host# edit vlan vlan-id
  5. Configure the bridge priority

    [edit ... protocols vstp vlan vlan-id]
    user@host# set bridge-priority bridge-priority

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

  6. Configure hello BPDU timers.

    1. Configure the maximum expected arrival time of hello BPDUs:

      [edit ... protocols vstp vlan vlan-id]
      user@host# set max-age seconds
    2. Configure the time interval at which the root bridge transmits configuration BPDUs:

      [edit ... protocols vstp vlan vlan-id]
      user@host# set hello-time seconds
  7. (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 vstp vlan vlan-id]
    user@host# set forward-delay seconds
  8. Configure the interfaces that participate in the VSTP instance.

    1. Enable configuration of the interface:

      [edit ... protocols vstp vlan vlan-id]
      user@host# edit interface interface-name
    2. Configure the interface priority:

      [edit ... protocols vstp vlan vlan-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 vstp vlan vlan-id interface interface-name]
      user@host# set cost interface-link-cost
    4. Configure the interface link mode to identify point-to-point links:

      [edit ... protocols vstp vlan vlan-id 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 vstp vlan vlan-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

    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.
  9. Verify the VSTP configuration:

    [edit]... { # Optional logical system and/or routing instanceprotocols {vstp {force-version stp; # Optional.interface interface-name {priority interface-priority;cost interface-link-cost; # Optional.mode (p2p | shared);edge; # Optional.}vlan vlan-id {bridge-priority bridge-priority;max-age seconds;hello-time seconds;forward-delay seconds; # Optional.interface interface-name {priority interface-priority;cost interface-link-cost; # Optional.mode (p2p | shared);edge; # Optional.}}}}}

Published: 2010-05-11