RSTP

Layer 2 Management > RSTP > Global Settings

• Select—click to select the context for which the configuration needs to be done.
• Context—displays the virtual context ID that uniquely represents a virtual switch created in the physical switch. This is a read-only field. This value ranges from 0 to 65535. The default value is 0.
• System Control—select the administrative shutdown status requested by management for the RSTP feature. The default option is Shutdown. The list contains:
  • Start—specifies that all resources required by RSTP should be allocated and RSTP should be supported in the device on all ports.
  • Shutdown—specifies that RSTP should be shutdown in the device on all ports and all allocated memory must be released.
  Note:

  The administrative status can be set as Shutdown, only if the RSTP Status is set as Disabled. The status can be set as Start, only if the MSTP System Control and PVRST System Control are set as Shutdown using the Layer 2 Management > MSTP > Global Configuration and Layer 2 Management > PVRST > Global Configuration screen respectively.

• Status—select the administrative module status requested by management for the RSTP module. RSTP provides rapid recovery of connectivity following the failure of a bridge/bridge port or a LAN. The default option is Disabled. The list contains:
  • Enabled—enables the RSTP in the device on all ports.
  • Disabled—disables the RSTP in the device on all ports.
  Note: RSTP can be enabled globally in the switch, only if the RSTP System Control status is set as Start.
• Dynamic Path Cost Calculation—select whether the dynamic path cost calculation is allowed. 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. According to the specification, path cost is calculated by dividing the speed with bandwidth of the segment connected to the port. 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. This field cannot be configured if the RSTP System Control is shut down or Status is set as Disabled.

• 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:

  This field can be configured only if System Control is set as Start. The manually assigned path cost is used irrespective of the status (True or False) of the dynamic path cost calculation.

• 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: This field can be configured only if System Control is set as Start.If the flush interval timer is set to zero, port based flushing occurs (default functionality). If it is set to non-zero, global / port based flushing occurs and is 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: This field can be configured only if System Control is set as Start.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 RSTP Traces screen

Layer 2 Management > RSTP > Global 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 > RSTP > Basic Settings

• Select—select the MSTP Instance ID for which the configuration needs to be applied.
• Context Id—displays the context ID.
• Priority—enter the priority value that is assigned to the switch. In RSTP, this value is used during the election of root. This value ranges from 0 to 61440. The default value is 32768. The values set for the priority must be in increments of 4096, e.g., 4096, 8192, 12288, etc
• Version—select the mode of STP in which the port is currently operating. The compatibility version allows the switch to operate temporarily (that is, till this configuration is reset manually) in other STP versions even though the spanning tree mode is set as some other version. This configuration is useful during cases where spanning tree mode itself is not required to be changed. The default option is RSTP Compatible. The list contains:
  • STP Compatible—specifies that the mode is set as STP compatible i.e. it transmits Config/TCN BPDUs.
  • RSTP Compatible—specifies that the mode is set as RSTP compatible i.e. it transmits RST BPDUs.
• Tx Hold Count—enter the transmit hold count which is the number of RST BPDUs that can be transmitted in a given interval. This value is configured to avoid flooding. Port transmit state machine uses this value to limit the maximum transmission rate. This value ranges from 1 to 10. The default value is 6.

• Max Age—enter the maximum expected arrival time (in seconds) of Hello BPDUs. STP information learned from network on any port is discarded, once the configured arrival time expires. The spanning tree topology is re-computed after this time interval. 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).

• 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 is 2.
• Forward Delay—enter the value that all bridges use for ForwardDelay when the bridge is acting as the root. This value is the number of seconds for which a port waits before changing from the blocking state to the forwarding state. This value ranges from 4 to 30 seconds. The default value is 15.

• Apply—modifies attributes and saves the changes.

Layer 2 Management > RSTP > 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).
  Note:

  Only the ports whose Admin State is set as Up are displayed.

• Port Role—displays the current role of the port for the spanning tree. The values can be:
  • Disabled—specifies that the port is disabled manually (RSTP Status) or automatically (Link). 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. It is blocked and not used for traffic. It is enabled and declared as the root port if the root port is blocked.
  • Backup—specifies that the port is acting as a backup path to a segment where another bridge port already connects. The port is blocked and not used for traffic, and it is enabled and declared as the 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 every segment.
• Port Priority—enter the priority value that is assigned to the port. This value is used during the Port Role selection process. This value ranges from 0 to 240. The default value is 128. This value should be set in steps of 16, e.g., 0, 16, 32, 48, etc.
• RSTP Status—select the administrative module status requested by management for the RSTP Module on the port. This enables or disables RSTP status of the port. The default option is Enable. The list contains:
  • Enable—enables RSTP in the device on the port. The port participates in the STP process and is ready to transmit/receive BPDUs and data.
  • Disable—disables RSTP in the device on the port. The port does not participate in the STP process and is not ready to transmit / receive BPDUs and data.
• Path Cost—enter the path cost that contributes to the path cost of paths containing the port. The paths’ path cost is used during calculation of shortest path to reach the 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.

• Protocol Migration—select the protocol migration state of the port. This is used for controlling of 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 RSTP BPDUs.
  • False—specifies that the port does not perform protocol migration mechanism. The port always transmits the standard RSTP BPDUs.
  Note: This field cannot be configured if the RSTP Status is set as Disable.The protocol migration triggers the transmission of RSTP BPDUs only once when set as True. The protocol migration changes automatically as False, once the RSTP BPDU is transmitted.
• Admin Edge Port—select the administrative status of the Edge Port parameter. The default option is False. The list contains:
  • True—sets the port as an edge port. The Port State is immediately set as forwarding. It is connected directly to a single end station. It allows RSTP 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 RSTP. It is connected to a routing device such as switch.
  Note:

  The value of the Edge Port parameter is automatically updated if the Auto Edge Detection is set as True

• Admin Point-to-Point—select the administrative 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 its members can be aggregated.
  • The MAC entity is configured for full Duplex operation, either manually or through auto negotiation process (negotiation Mode is set as Auto).

• Auto Edge Detection—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. This overrides the value set in the field Admin Edge Port, based on the reception of BPDU.
  • False—specifies that automatic detection of edge port is disabled. This uses the manually configured value for the Edge Port parameter.
• 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 topology 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 port.
• 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 RSTP BPDUs. The default option is True. The list contains:
  • True—normally processes the RSTP BPDUs received on the port.
  • False—discards the RSTP 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 RSTP BPDU are transmitted from the port.
  • False—specifies that RSTP BPDUs transmission is blocked from the port.
  Note: This field should be set as False for ports to be configured as Layer-2 Gateway 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.
  Note:

  BPDU Transmit, Restricted Role and Restricted TCN should be set as False before configuring the port as a Layer 2 gateway port. L2GP operates similarly to that of the normal port operation but pretends to continuously receive BPDUs when Admin State is set to Up.

• 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 topology, 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.
  Note:

  The root guard feature can be enabled only for the ports whose Switch Port Mode is configured as Trunk using Layer 2 Management > Port Manager > Port Basic Settings screen.

• BPDU Guard—the administrative status for the BPDU guard feature in the port. This feature configures BPDU guard globally in RSTP 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 > RSTP > 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
• Designated Cost—displays the Path Cost of the Designated Port of the segment connected to the port. This value ranges from 1 to 200000000.
• 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 and represents the port through which the Designated Bridge forwards frames. This value is a 2-byte octet string e.g. 80:05.
• Type—displays the operational Admin Point to Point of the LAN segment attached to the port. The values can be:
  • Point-to-point—specifies that the port is treated as if it is connected to a point-to-point link..
  • SharedLan—specifies that the 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.