Spanning Tree Bridge Property

The Spanning Tree Protocol (STP) is a network protocol that ensures a loop-free topology for any bridged Ethernet local area network. The basic function of STP is to prevent bridge loops and the broadcast radiation that results from them. The Spanning Tree allows a network design to include spare (redundant) links to provide automatic backup paths if an active link fails, without the danger of bridge loops, or the need for manual enabling/disabling of these backup links.

Spanning Tree Protocol (STP) is standardized as IEEE 802.1D. As the name suggests, it creates a spanning tree within a mesh network of connected layer-2 bridges (typically Ethernet switches), and disables those links that are not part of the spanning tree, leaving a single active path between any two network nodes.

The following sections describe how to view the properties of an Optical Line Terminal (OLT) configured to support STP.

Configuration

  1. Logon to EMS and in the Network common tree, right-click on the target OLT and select Protocol on the dropdown list, then select Spanning tree on the dropdown list.

  2. The Spanning Tree Bridge Property dialog displays, with the Configuration data displayed.

  3. Refer to the following table for a description of the Spanning Tree Bridge Protocol configuration attributes.

 

Attribute

Description

Notes
Protocol Configuration
Protocol Version Determines the protocol used for Spanning Tree Protocol. STP (802.1d)
RSTP (802.1w)
MSTP (802.1s)
CST Configuration
Bridge Property Used to bias the selection of Root Bridge by the spanning tree protocol.

Valid Bridge Priorities are in the range 0 through 61440, in steps of 4096.

Bridge Max Age (secs)

Maximum age of the information transmitted by the bridge. The Max Age timer is zeroed when BPDUs are received. When it expires, it causes a port to update the state of the port to Designated and will go through the listening and learning state to the forwarding state.

Range 6 to 40 seconds.

Default 20 seconds.

Bridge Forward Delay (secs)

Time spent in the listening and learning states of the STP protocol machine.

Range 4 to 30 seconds.

Default 15 seconds

Bridge Hello Time (secs)

BPDUs are sent at a minimum every Hello Time interval. The Hello Time cannot be modified.

Range 1 to 2 seconds. Default 2 seconds.

Bridge Hold Count

Defines the maximum number of BPDUs that can be transmitted during every Hello Time period.

Range 1 to 10. Default 6.

Max Hops

Maximum number of Hops that the BPDUs can travel within the L2 network.

Range 6 to 40. Default 20.

MST Configuration

Configuration Name

Variable-length text string encoded within a fixed field of 32 octets. If less than 32 octets, the text string should be terminated by the NULL character with the remainder of the field filled with NULL characters.

 

Revision

Unsigned integer encoded within a fixed field of 2 octets.

 

MSTI

List of MSTD values that are currently supported by the bridge.

Up to eight (8) MSTIs can be configured.

ID

MSTI value corresponding to the VLAN Identifier (VID).

Range 0 through 4094

Priority

Priority assigned to the respective MSTID.

 

 

  1. Change, as required, the STP values, then click the Apply button.
  2. Click the Close button to dismiss the Spanning Tree Bridge Property dialog.

Status

Use the following procedure to view the STP bridge property statistics.

  1. Logon to EMS and in the Network common tree, right-click on the target OLT and select Protocol on the dropdown list, then select Spanning tree on the dropdown list.

  2. Click on the Status tab. The Status of this instance is displayed.

  3. Refer to the following table for a description of the Spanning Tree Bridge Protocol configuration attributes.
     

    Attribute

    Description

    Notes
    CST Status
    Configuration Digest Configuration assigned this bridge.  
    Time Since TCN Amount of days, hours, minutes and seconds since topology change notification.  
    Designated Root    
    Interval between periodic transmissions of configuration messages by designated ports.    

    TCN Count

    Topology Change Notification count

     

    Root Path Cost

    Cost of Root path

     

    Root Port

    A Root Port is a designated port on a switch with the least Path Cost to a bridge.

     

    CST Path Cost

    Cost of CST path

     

    Bridge Forward Delay (secs)

    Delay used by STP bridge to transition root and designated ports to forwarding.

     

    Bridge Max Age (secs)

    Maximum age of the information transmitted by the bridge when it is the root bridge.

     

    MST Status

    MSTI

    List of MSTD values that are currently supported by the bridge.

    Up to eight (8) MSTIs can be configured.

    Bridge ID

    Identification of the bridge

     

    Time since TCN

    Amount of days, hours, minutes and seconds since last topology change notification.

     

    Designated Root

    Interval between periodic transmissions of configuration messages by designated ports.

     

    TCN Count

    Topology Change Notification count

    .

    Root Port

    Maximum number of hops allowed for this bridge.

     
  4. Click on Previous or Next buttons to view MSTI instances.
  5. Click the Close button to close the Spanning Tree Bridge Property dialog.