MSTP

Layer 2 Management > MSTP > Basic Settings

• Select—click to select the context for which the configuration needs to be done.
• Context Id—displays the virtual context ID that uniquely represents a virtual switch created in the physical switch. This value ranges from 0 to 65535. The default value is 0.
• System Control—select the administrative shutdown status requested by management for the MSTP module. The default option is Start for the default context and shutdown for the other contexts. The list contains:
  • Start—specifies that MSTP is active in the device on all ports.
  • Shutdown—specifies that MSTP is shutdown in the device on all ports, and all allocated memory is release
  Note:

  The administrative status can be set as Shutdown, only if the MSTP Status is set as Disabled. The status can be set as Start, only if the RSTP System Control and PVRST System Control are set as Shutdown using the Layer 2 Management > RSTP > Global Configuration and Layer 2 Management > PVRST > Global Configuration screen respectively. MSTP System Control cannot be shutdown if MSTP status is enabled.

• MSTP Status—select the administrative status requested by management for the MST feature. MSTP is used to configure spanning tree on per VLAN basis or multiple VLANs per spanning tree. It provides multiple forwarding paths for data traffic and enables load balancing. The default option is Enabled for the default context and Disabled for the other contexts. The list contains:
  • Enabled—enables MST in the device on all ports.
  • Disabled—disables MST in the device on all ports
  Note:

  To enable MSTP globally in the switch, the MSTP System Control status should be set as Start. All fields in this screen (except System Control) are greyed out and cannot be configured, once the MSTP status is set as Disabled.

• Maximum MST Instances—enter the maximum number of spanning trees to be allowed in the switch. This value represents the maximum number of active MSTIs (MST Instances) that can be created. This allows the user to limit the number of spanning tree instances to be allowed in the switch. This does not count the special MSTID such as PTETID (Provider Backbone Bridging—Traffic Engineering Multiple Spanning Tree ID), which is used to identify VIDs used by Ethernet switched paths (ESPs). This value ranges from 1 to 64. The default value is 64.
  Note:

  The maximum available number of instances is 16 (values from 0–15 where 0 being CIST).

• Bridge Priority—enter the priority value that is assigned to the switch. This value is used during the election of CIST root, CIST regional root and, IST root. This value ranges from 0 to 61440. The default value is 32768. The values set for Bridge Priority must be in steps of 4096.

• Protocol Version—select the version of STP in which the switch is currently running. This allows the user to set the type of STP to be used by the switch to form loop-free topology. The default option is MSTP. The list contains:
  • STP—sets the version as STP specified in IEEE 802.1D.
  • RSTP—sets the version as RSTP as specified in IEEE 802.1w.
  • MSTP—sets the version as MSTP as specified in IEEE 802.1s.
  Note:

  The Fields Region Name and Region Version are greyed out and cannot be configured, if the protocol version is set as STP or RSTP.

• Region Name—enter the name for the region’s configuration to identify the specific MST region. Each MST region contains multiple spanning tree instances and runs special instance of spanning tree known as IST for disseminating of STP topology information for other STP instances. The default value is same as that of the Switch Base MAC Address configured in the Factory Default Settings screen. This value is an octet string of maximum size 32.
  Note:

  This field can be configured only if the protocol version is selected as MSTP.

• Region Version—enter the version that represents the specific MST region. The default value is 0. This value ranges from 0 to 65535.
  Note:

  This field can be configured only if the protocol version is selected as MSTP.

• Dynamic Path Cost Calculation—select whether the dynamic path cost calculation is allowed or not. The path cost represents the distance between the root port and designated port. The path cost is based on a guideline established as part of 802.1d. The path cost is dynamically calculated using port speed, when the operational status of the port changes from down to up or link speed at the time of port creation. The default option is False. The list contains:
  • True—dynamically calculates path cost based on the speed of the ports whose Admin State is set as Up at that time. The path cost is not changed based on the operational status of the ports, once calculated.
  • False—dynamically calculates path cost based on the link speed at the time of port creation
  Note:

  The manually assigned path cost is used irrespective of the status (True or False) of the dynamic path cost calculation.

• Speed Change Path Cost Calculation—select whether the speed change path cost calculation is allowed or not. The speed change path cost is to be calculated for ports whose speed changes dynamically. This feature is mainly used for Link Aggregation ports whose speed changes due to the addition and deletion of ports from the port channel. The default option is False. The list contains:
  • True—specifies that path cost is dynamically calculated for ports based on their speed at that time. It is calculated if the speed of the port changes.
  • False—specifies that path cost is not dynamically calculated for ports based on their speed at that time.
  Note:

  The manually assigned path cost is used irrespective of the status (True or False) of the path cost calculation if Path Cost for the port is manually assigned.

• Flush Interval—enter the value that controls the number of flush indications invoked from spanning-tree module per instance basis. This value ranges from 0 to 500 centi-seconds. The default value is 0.
  Note: If the flush interval timer is set to zero, port and instance based flushing occurs (default functionality). If it is set to non-zero, instance based flushing occurs (dependent on the flush-indication-threshold value).
• Flush Indication Threshold—enter the number of flush indications to go before the flush-interval timer method triggers. This value ranges from 0 to 65535. The default value is 0.
  Note: The flush indication threshold value can be configured only when flush interval value is other than default value. When flush indication threshold is default value and flush interval is non-default value, instance based flushing occurs during the first flush indication trigger. When the flush indication threshold value is non-default(x) and flush-interval value is non-default, port & instance based flushing is triggered until the threshold(x) is reached. Once the threshold is reached, instance based flushing is triggered & timer starts.
• BPDU Guard—select the administrative status for the BPDU guard feature in the port. This feature configures BPDU guard globally in MSTP. This global BPDU is applicable if and only no port specific BPDU Guard is configured. The default option is Disable. The list contains:
  • Enabled—enables BPDU Guard feature on edge ports globally and moves the port to disabled discarding state when BPDU is received on the edge ports
  • Disabled—disables BPDU Guard feature on edge ports globally.

• Apply—modifies attributes and saves the changes.
• Configure Trace Options—click to access the MSTP Traces screen.

Layer 2 Management > MSTP > Basic Settings > Global Configuration screen.

Click Configure Trace Options.

• Traces—select the traces for which debug statements is to be generated. The options are:
  • Init-Shut—generates debug statements for init and shutdown traces. This trace is generated on failed and successful initialization and shutting down of STP related module and memory.
  • Management—generates debug statements for management traces.
  • Memory—generates debug statements for memory related traces. This trace is generated on failed and successful allocation of memory for STP process.
  • BPDU—generates debug statements for BPDU related traces. This trace is generated on failed and successful reception, transmission and processing of BPDUs.
  • Events—generates debug statements for event handling traces. This trace is generated to denote events that are posted to STP configuration queue whenever you configure any of the STP features.

• Traces—the options are (cont):
  • Timer—generates debug statements for timer module traces. This trace is generated on failed and successful start, stop and restart of STP timers. The different STP timers are:
    • Forward delay timer
    • Hello timer
    • Migration delay timer
    • Recent backup while timer
    • Received information while timer
    • Recent root while timer
    • Topology change timer
    • Hold timer
    • Edge delay timer
    • Rapid age duration timer
    • Pseudo information hello timer
  • Redundancy—generates debug statements for redundancy code flow traces. This trace is generated in standby node STP while taking backup of configuration information from active node.
  • Semaphore—generates debug statements for state machine variable changes traces. This trace is generated on failed and successful creation and deletion of semaphore.
  • Errors—generates debug statements for all failure traces of the traces.
• State Machine—select the SEMs (State Event Machines) for which debug statements are to be generated to denote the event and state of the selected SEM. The options are:
  • Port-Info—generates debug statements for port information SEM.
  • Port-Receive—generates debug statements for port receive SEM.
  • Port-Role-Select—generates debug statements for role selection SEM.
  • Role-Transition—generates debug statements for role transition SEM.
  • State-Transition—generates debug statements for state transition SEM.
  • Protocol-Migration—generates debug statements for protocol migration SEM.
  • Topology-Change—generates debug statements for topology change SEM.
  • Port-Transmit—generates debug statements for port transmit SEM.
  • Bridge-Detection—generates debug statements for bridge detection SEM.
  • Pseudo-Info—generates debug statements for port receive pseudo information SEM.

• Apply—modifies attributes and saves the changes.
• Configure Global Options—accesses Global Configuration screen

Layer 2 Management > MSTP > Timers

• Select—click to select the context for which the configuration needs to be applied.
• Context Id—displays the context ID.
• Maximum Hop Count—enter the maximum hop count value that represents the maximum number of switches that a packet can cross before it is dropped. This value is used by the switch to avoid infinite looping of the packets, if it is selected as the root switch in the topology. This value ranges from 6 to 40. The default value is 20. The root switch always transmits a BPDU with the maximum hop count value. The receiving switch decrements the value by one and propagates the BPDU with modified hop count value. The BPDU is discarded and the information held is aged out, when the count reaches 0.
• Max Age—enter the amount of time a port waits for STP/RSTP information. This value is used by MSTP while interacting with STP/RSTP domains on the boundary ports. This value ranges from 6 to 40 seconds. The default value is 20.
  Note:

  The maximum age should be lesser than or equal to 2*(Forward Delay—1.0) and should be greater than or equal to 2* (HelloTime + 1.0).

• Forward Delay—enter the number of seconds a port waits before changing from the learning/listening state to the forwarding state. This value ranges from 4 to 30 seconds. The default value is 15.
• Transmit Hold Count—enter the value used by the port transmit state machine for limiting the maximum transmission rate i.e. the number of packets that can be sent for a given interval. This value is configured to avoid flooding. Port transmit state machines use this value to limit the maximum transmission rate. This value ranges from 1 to 10. The default value is 6.

• Hello Time—enter the amount of time between the transmission of configuration bridge PDUs by this node. This value can be either 1 or 2 seconds. The default value is 2.

• Apply—modifies attributes and saves the changes.

Layer 2 Management > MSTP > Port Configuration

• Select—click to select the port for which the configuration needs to be applied.
• Port Id—displays the port, which is a combination of interface type and interface ID. The interface ID is a combination of a slot number and a port number (slot number/port number).
• Path Cost—enter the value that contributes to the path cost of paths towards the CIST Root which includes this port. The paths’ path cost is used during calculation of shortest path to reach the CIST root. The path cost represents the distance between the root port and designated port. This value ranges from 1 to 200000000. The default value is 200000 for all physical ports and 199999 for port channels.
  Note:

  The default value is used as path cost if this field is not configured and the Dynamic Path Cost Calculation and Speed Change Path Cost Calculation are set as False. The dynamically calculated path cost is used if the path cost is not manually configured and one of these Fields is set as True.The configured value is used as the path cost irrespective of the status (True or False) of the Dynamic Path Cost Calculation and Speed Change Path Cost Calculation.

• Priority—enter the priority value that is assigned to the port. This value is used during the role selection process. The four most significant bits of the Port Identifier of the Spanning Tree instance can be modified by setting the CIST Port Priority value. The values that are set for Port Priority must be in steps of 16. The Priority value ranges from 0 to 240. The default value is 128.

• Point-to-Point Status—select the point-to-point status of the LAN segment attached to the port. The default option is Auto. The list contains.
  • ForceTrue—specifies that port is connected to a point-to-point link.
  • ForceFalse—specifies that port is having a shared media connection.
  • Auto—specifies that the ports as having a shared media connection, or a point-point link based on the prevailing conditions.
  Note:

  Port is considered to have a point-to-point link if:

  • It is an aggregator and all of its members can be aggregated.
  • The MAC> entity is configured for full Duplex operation, either manually or through auto negotiation process (that is, negotiation Mode is set as Auto).
• Edge Port—select the administrative value of the Edge Port parameter. The default option is False. The list contains:
  • True—sets the port as an edge port (then Port State is immediately set as forwarding). It is connected directly to a single end station. It allows MSTP to converge faster and does not wait to receive BPDUs.
  • False—sets the port as a non-Edge port (the spanning tree process is performed using the MSTP). It is connected to a routing device such as a switch.
• MSTP Status—select the MSTP status of the port for all spanning tree instances. This value will override the port’s status in the MSTI contexts. The default option is Enable. The list contains:
  • Enable—enables MST in the port. MAC frames are forwarded, and their source addresses are learnt.
  • Disable—disables MST in the ports. MAC frames are not forwarded, and their source addresses are not learnt.
• Protocol Migration—select the protocol migration state of the port. This is used to control the protocol migration mechanism that enables the module to interoperate with legacy 802.1D switches. The default option is False. The list contains:
  • True—specifies that the port transmits BPDUs based on the spanning tree protocol supported by the receiving switch. The port is forced to transmit MSTP BPDUs without instance information.
  • False—specifies that the port does not perform protocol migration mechanism. The port always transmits the standard MSTP BPDUs.
  Note:

  The protocol migration is greyed out and cannot be configured, if the MSTP Status is set as Disable.

• Hello Time—enter the amount of time between the transmission of Configuration bridge PDUs by this node in units of hundredths of a second. This value can be either 1 or 2 seconds. The default value is 2.

• Auto Edge Status—select whether the Edge Port parameter of the port is detected automatically or configured manually. The default option is True. The list contains:
  • True—specifies that detection of port as Edge Port happens automatically.
    • The port is set as edge port if no BPDU is received on the port.
    • The port is set as non-edge port, if any BPDU is received by that port.
    Note:

    This overrides the value set in the field Edge Port, based on the reception of BPDU.

  • False—specifies that the auto edge feature is disabled and the manually configured value for the Edge Port parameter is used.
• Restricted Role—select whether the selection of port Role as root can be blocked during the role Selection process. This feature allows the user to block switches external to a core region of the network from influencing the spanning tree active topology. The default option is False. The list contains:
  • True—blocks the port from being selected as root port for the CIST or any MSTI, even if it has the best spanning tree priority vector. It is selected as an alternate port after the root port is selected.
    Note:

    The blocking of port from being selected as a root port may cause lack of spanning tree connectivity.

  • False—includes all available ports of the topology, in the root selection process to select the root for CIST or any MSTI.
• Restricted TCN—select the status of transmission of the received topology change notifications and topology changes to the other ports in the network. This feature allows the user to block switches external to a core region of the network from causing address flushing in the region. The default option is False. The list contains:
  • True—blocks the port from propagating the received topology change notifications and topology changes to other ports.
    Note:

    The blocking of port may cause temporary loss of connectivity after changes in a spanning tree active topology as a result of persistent incorrectly learnt station location information.

  • False—allows the port to propagate the received topology change notifications and topology changes to other ports.
• BPDU Receive—select the processing status of the received MSTP BPDUs. The default option is True. The list contains:
  • True—normally processes the MSTP BPDUs received on the port.
  • False—discards the MSTP BPDUs received on the port.
• BPDU Transmit—select the BPDU transmission status of the port. The default option is True. The list contains:
  • True—specifies that MSTP BPDUs are transmitted from the port.
  • False—specifies that MSTP BPDUs transmission is blocked from the port

• Layer 2-Gateway Port—select whether the port acts as a normal port or as a L2GP The default option is False. The list contains:
  • True—specifies that the port operates as a Layer 2 Gateway Port.
  • False—specifies that the port operates as a normal port.

• Loop Guard—select the status of loop guard. The Loop Guard does age out the information even if the peer does not send information. If the port continues to receive information through BPDUs, the operation on this port will be normal. This is useful when the neighbor bridge is faulty; that is, the bridge cannot send BPDUs but continues to send data traffic. The default option is False. The list contains:
  • True—enables the loop guard in the port.
  • False—disables the loop guard in the port.
• Root Guard—select the administrative status for the root guard feature in the port. When enabled, this feature causes the port not to be selected as Root Port for the CIST or any MSTI, even if it has the best spanning tree priority vector. Such a Port will be selected as an Alternate Port after the Root Port has been selected. The default option is Disabled, and this can cause lack of spanning tree connectivity. It is set by a network administrator to prevent bridges external to a core region of the network influencing the spanning tree active topology; possibly because those bridges are not under the full control of the administrator.
  • Enabled—enables root guard feature in the port.
  • Disabled—disables root guard feature in the port.
• BPDU Guard—the administrative status for the BPDU guard feature in the port. This feature configures BPDU guard globally in MSTP and this global BPDU is applicable if and only if no port specific BPDU Guard is configured. The default option is Disable. The list contains:
  • Enabled—enables BPDU Guard feature on edge ports globally and moves the port to disable discarding state when BPDU is received on the edge ports
  • Disabled—disables BPDU Guard feature on edge ports globally.
• Error Recovery—enter the amount of time to bring the interface out of the error-disabled (err-disabled) state. This value ranges from 30 to 65535 seconds. The default value is 30.

• Apply—modifies attributes and saves the changes.

Layer 2 Management > MSTP > VLAN Mapping

• Select—select the instance Id for which the mapping is to be deleted.
• MSTP Instance ID—enter an integer value that is used to uniquely identify an instance of the MSTP. This value ranges from 1 to 64. The special value 4094 is used in a switch that supports PBB-TE. This special value represents PTETID that identifies VID used by Ethernet switched paths (ESPs).
  Note:

  The MSTP Instance ID depends on the Maximum MSTP instance configured in the Global Configuration page. Any external agent can separately provide ESPs. The ESPs do not use spanning tree.

• Add VLAN—select the VLAN that should be mapped to the MSTP instance. The list contains VLAN Name of all VLANs available in the switch. The mapping of VLAN to the MSTP instance is not done again if the VLAN is already mapped to that instance.
• Delete VLAN—select the VLAN that should be unmapped from the MSTP instance. The list contains VLAN Name for the VLANs available in the switch. The unmapping of VLAN from the MSTP instance cannot done if the VLAN is already unmapped from that instance.
• Mapped VLANs—displays the VLAN ID mapped to the spanning tree instance specified. All Instance Specific information for the member ports of the VLAN will be created.

• Add—adds and saves new configuration
• Reset—resets to default value for respective fields and discards all user inputs
• Deleted—deletes the selected entry

Layer 2 Management > MSTP > Port Settings

• Select—click to select the port for which the configuration needs to be applied.
• Port—displays the port, which is a combination of interface type and interface ID. The interface ID is a combination of a slot number and a port number (slot number/port number).
• MSTP Instance ID—enter an integer value that is used to uniquely identify an instance of the MSTP. This value ranges from 1 to 64. The special value 4094 is used in a switch that supports PBB-TE. This special value represents PTETID that identifies VID used by Ethernet switched paths (ESPs).
  Note:

  This field displays the Instance ID created using the VLAN Mapping screen. The maximum available number of instances will be 16 (values from 0–15 where 0 being CIST).

• Port State—select the status of the MSTP in the port. The list contains:
  • Enabled—enables MSTP in the port. The port participates in the STP process and is ready to transmit/receive BPDUs and data.
  • Disabled—disables MSTP in the port. The port does not participate in the STP process and is not ready to transmit/receive BPDUs and data
• Priority —enter the priority value that is assigned to the port. This value is used during the role selection process. The four most significant bits of the Port Identifier of the Spanning Tree instance can be modified by setting the CIST Port Priority value. The values that are set for Port Priority must be in steps of 16. This value ranges from 0 to 240. The default value is 128.
• Cost—enter the value that contributes to the path cost of paths towards the CIST Root which includes this port. The paths’ path cost is used during calculation of shortest path to reach the MSTI root. The path cost represents the distance between the root port and designated port. This value ranges from 0 to 200000000.The default value is 200000 for all physical ports and 199999 for port channels.

• PseudoRootId Priority—enter the priority of the pseudo root. This value is used by a port configured as L2GP, and the field Layer 2-Gateway Port is set as True. This value ranges from 0 to 61440. The default value is 32768. The value should be set in steps of 4096; that is, you can set the value as 0, 4096, 8192, 12288, and so on.
• PsuedoRootId Address—enter the unicast MAC address of the pseudo root. This value is used by port configured as L2GP (the field Layer 2-Gateway Port is set as True). The default value is 00:08:02:03:04:01.

• Apply—modifies attributes and saves the changes.

Layer 2 Management > MSTP > CIST Port Status

• Port—displays the port, which is a combination of interface type and interface ID. The interface ID is a combination of a slot number and a port number (slot number/port number).
• Designated Root—displays the unique identifier of the bridge recorded as the CIST root in the transmitted configuration BPDUs. This value is an 8-byte octet string. For example, 80:00:00:01:02:03:04:05
• Root Priority—displays the Bridge Priority configured in Global Configuration Screen that represents the priority of the bridge recorded as the CIST root in the configuration BPDUs transmitted. This value ranges from 0 to 61440. The default value is 32768.
• Designated Bridge—displays the unique identifier of the bridge, which the port considers to be the designated bridge for the port's segment. The designated bridge is the only bridge allowed to forward frames to and from the segment. This value is an 8-byte octet string. For example, 80:00:00:01:02:03:04:05.

• Designated Port—displays the identifier of the port on the Designated Bridge for the port's segment. This represents the port through which the Designated Bridge forwards frames to and from the segment. This value is a 2-byte octet string. For example, 80:05.
• Designated Cost—displays the identifier of the port on the Designated Bridge for the port's segment. This represents the port through which the Designated Bridge forwards frames to and from the segment. This value is a 2-byte octet string. For example, 80:05.
• Regional Root—displays the unique identifier of the bridge recorded as the CIST regional root in the configuration BPDUs transmitted. This value is an 8-byte octet string. For example, 80:00:00:01:02:03:04:05
• Regional Root Priority—displays the Bridge Priority that represents the priority of the bridge recorded as the CIST regional root in the configuration BPDUs transmitted. This value ranges from 0 to 61440. The default value is 32768.
• Regional Path Cost—displays the port’s Path Cost that contributes to the cost of paths (including the port) towards the CIST Regional Root. This value ranges from 1 to 200000000.
• Type—displays the operational Point-to-Point Status of the LAN segment attached to the port. The values can be:
  • Point-to-point—port is treated as if it is connected to a point-to-point link.
  • SharedLan—port is treated as if it is having a shared media connection.

• Role—displays the current role of the port for the spanning tree instance. The values can be:
  • Disabled—specified that the port is disabled manually (Port State) or automatically (Link status in Layer 2 Management > Port Manager > Basic Settings). It does not take part in the spanning tree process.
  • Alternate—specifies that the port is acting as an alternate path to the root bridge (i.e. it is blocked and not used for traffic). The alternate port is enabled and declared as a root port if the current root port is blocked.
  • Backup—specifies that the port is acting as a backup path to a segment where another bridge port already connects (i.e. it is blocked and not used for traffic). The backup port is enabled and declared as a designated port if the active designated port is blocked.
  • Root—specifies that the port is used to forward data to root bridge directly or through an upstream LAN segment.
  • Designated—specifies that the port is used to send and receive packets to/from a specific downstream LAN segment/device. Only one designated port is assigned for each segment.

• Port State—displays the current state of the port as defined by the common STP. The values can be:
  • Disabled—specifies that the port is disabled manually (Port State) or automatically (Link). It does not take part in the spanning tree process.
  • Discarding—specifies that the port is in Discarding state i.e. No user data is sent over the port.
  • Learning—specifies that the port is in the Learning state i.e. the port is not forwarding frames yet, but is populating its MAC-address-table by learning source addresses from received frames and storing them in the switching database for using these details while sending and receiving data.
  • Forwarding—specifies that the port is in Forwarding state i.e. the port is operational by sending and receiving data based on the formed spanning tree topology which is loop-free.

Layer 2 Management > MSTP > Bridge Priority

• Select—select the MSTP Instance ID for which the configuration needs to be applied.
• MSTP Instance ID—displays the integer value that uniquely identifies an instance of the MSTP. This value ranges from 1 to 64. The special value 4094 is used in a switch that supports PBB-TE. This special value represents PTETID that identifies VID, which can be used by ESPs.
  Note:

  This value is the instance ID created using the VLAN Mapping screen.Any external agent can separately provide ESPs. The ESPs do not use spanning tree.

• Root—select the root type for the given VLAN interface. The list contains:
  • primary—configures the switch to become root for a given VLAN. The priority of the switch is lowered until it becomes root
  • secondary—configures the switch to become backup root for a given VLAN. The priority of the switch is lowered until it becomes one priority higher than the root, so it can become root if the current root fails.
• Bridge Priority—denter the priority value that is assigned to the switch. This value is used during the election of CIST root, CIST regional root, and IST root. This value ranges from 0 to 61440. The default value is 32768.
  Note:

  The value should be set in increments of 4096. For example, 0, 4096, 8192, 12288, and so on.

• Bridge Cost—displays the Cost of the path to the MSTI Regional Root seen by this bridge. This is a read-only field
• Root Port—displays the port number of the port which offers the lowest path cost from this bridge to the CIST Root Bridge. This is a read-only field

• Apply—modifies attributes and saves the changes.