Configuring CIST ports for MSTP

Configure Common and Internal Spanning Tree (CIST) ports to configure ports for MSTP.

Procedure

In the navigation tree, expand the following folders: Configuration > VLAN > Spanning Tree.
Click MSTP.
Click the CIST Port tab.

Note

The MSTP, CIST Port tab contains information for each port that is common to all bridge and spanning tree instances.
Use the fields in the CIST Port box to configure the MSTP CIST port.
Click Apply.

CIST Port field descriptions

Use the data in the following table to use the CIST Port tab.


Name	Description
Port	Specifies the port number of the port for which this entry contains spanning tree information.
PathCost	Specifies the contribution of this port to the path cost of paths towards the CIST root that includes this port.
Priority	Specifies the four most significant bits of the port identifier of the spanning tree instance which are modified by setting the CistPortPriority value. The values that are configured for port priority must be in steps of 16. Although port priority values can range from 0 to 255, only the following values are used: 0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224, 240. The default is 128.
DesignatedRoot	Specifies the unique bridge identifier of the bridge recorded as the CIST root in the configuration BPDUs transmitted.
DesignatedCost	Specifies the path cost of the designated port of the segment that connects to this port.
DesignatedBridge	Specifies the unique bridge identifier of the bridge which that port considers to be the designated bridge for the ports segment.
DesignatedPort	Specifies the port identifier of the port on the designated bridge for this port segment.
RegionalRoot	Specifies the unique bridge identifier of the bridge recorded as the CIST regional root identifier in the configuration BPDUs transmitted.
RegionalPathCost	Specifies the contribution of this port to the path cost of paths towards the CIST regional root that include this port.
ProtocolMigration	Indicates the protocol migration state of this port. If you chose true, the option initiates protocol migration for a port. If you chose false, the option terminates protocol migration for a port. An MSTP-compatible port transmits and receives only RSTP BPDUs. If an MSTP port receives an STP BPDU, it becomes an STP port. User intervention is required to change this port back to MSTP mode. This process is called Port Protocol Migration. You must configure protocol migration to true on all spanning-tree enabled interfaces when you change the spanning tree version from STP-compatible to MSTP for those interfaces to work in the proper mode.
AdminEdgeStatus	Specifies the administrative value of the Edge Port parameter. A value of true indicates that this port is an edge-port, and a value of false indicates that this port is a nonedge-port.
OperEdgeStatus	Specifies the operational value of the Edge Port parameter. The object is initialized to the value of AdminEdgeStatus and is configured to false on reception of a BPDU.
AdminP2P	Specifies the administrative point-to-point status of the LAN segment attached to this port. A value of forceTrue indicates that this port is treated as if it connects to a point-to-point link. A value of forceFalse indicates that this port is treated as having a shared media connection. A value of auto indicates that this port is considered to have a point-to-point link if it is an aggregator and all of its members are aggregatable, or if the MAC entity is configured for full-duplex operation, either through autonegotation or by management means.
OperP2P	Specifies the operational point-to-point status of the LAN segment attached to this port. It indicates whether a port is considered to have a point-to-point connection or not. The value is determined by management or by autodetection as described in the AdminP2P object.
HelloTime	Specifies the amount of time in hundredths of a second between the transmission of configuration bridge PDUs by this node on this port.
OperVersion	Indicates whether the port is operationally in the MSTP mode, the RSTP mode, or the STP-compatible mode; that is, whether the port transmits MST BPDUs, RST BPDUs, or Config/TCN BPDUs. Although STP and MSTP are variations of the same spanning tree protocol, they communicate information differently. A switch in MSTI mode cannot recognize the spanning tree groups running on a chassis configured with STP. MSTP spanning tree groups are not the same as STP spanning tree groups. Using a switch in MSTP mode with another chassis in STP mode can create a loop in the network.
EffectivePortState	Specifies the effective operational state of the port for CIST. This is true only if the port is operationally up at the interface and protocol levels for CIST. This is configured to false for all other conditions.
State	Specifies the current state of the port as defined by the common spanning tree protocol. It can be disabled, discarding, learning, or forwarding.
ForcePortState	Specifies the current state of the port. You can change the port to either Disabled or Enabled for the base spanning tree instance.
SelectedPortRole	Specifies the selected port role of the port for this spanning tree instance.
CurrentPortRole	Specifies the current port role of the port for this spanning tree instance.