Field descriptions in MSTP debug command output

The following table contains descriptions of the debugging information displayed in the output of show spanning-tree debug-counters commands.

MSTP debug command output: field descriptions

Field

Displays the number of...

Invalid BPDUs

Received BPDUs that failed standard MSTP (802.1Q-REV/D5.0 14.4) validation checks and were dropped. This counter is maintained by the CIST (default MST instance 0) on a per-port basis.

Errant BPDUs

Received BPDUs that were dropped on a port that is configured to not expect BPDU packets. This counter is maintained by the CIST (MST instance, 0default MST instance 0 in the network) on a per-port basis and is incremented each time a BPDU packet is received on a port configured with the BPDU filter to ignore incoming BPDU packets (spanning-tree bpdu-filter command) or the BPDU protection feature to disable the port when BPDU packets are received (spanning-tree bpdu-protection command).

MST Config Error BPDUs

BPDUs received from a neighbor bridge with inconsistent MST configuration information. For example, BPDUs from a transmitting bridge may contain the same MST configuration identifiers (region name and revision number) and format selector as the receiving bridge, but the value of the Configuration Digest field (VLAN ID assignments to regional IST and MST instances) is different. This difference indicates a probable configuration error in MST region settings on the communicating bridges. The received BPDU is still processed by MSTP.

This counter is maintained by the CIST (default MST instance 0) on a per-port basis.

Looped-back BPDUs

Times a port has received self-sent BPDU packets as the result of an external loop condition in which the BPDUs were looped back to the originating transmission port. The received BPDU is still processed by MSTP and the port changes to a blocked state.

This counter is maintained by the CIST (default MST instance 0) on a per-port basis.

Starved BPDUs

Times that no BPDUs are received within the scheduled interval (three times the Hello Time value configured with the spanning-tree hello-time command) from a downstream CIST-designated peer port on the CIST root, alternate, or backup port. As a result, the "starved" port triggers a spanning tree topology regeneration.

This counter is maintained by the CIST (default MST instance 0) on a per-port basis.

Starved MSTI MSGs

Times that no BPDUs are received within the scheduled interval (three times the Hello Time value configured with the spanning-tree hello-time command) from a downstream MSTI-designated peer port on the MSTI root, alternate, or backup port. As a result, the "starved" port triggers a spanning tree topology regeneration.

This counter is maintained by the CIST (default MST instance 0) on a per-port basis.

Exceeded Max Age BPDUs

Times that a BPDU packet is received from a bridge external to the MST region with a Message Age value greater than the configured value of the Max Age parameter (spanning-tree maximum age command). This may occur if the receiving bridge is located too far from the root bridge (beyond the configured size of the spanning tree domain on the root bridge) or if a BPDU packet with invalid root information is continuously circulating between bridges in a spanning tree domain and needs to be aged out.

This counter is maintained by the CIST (default MST instance 0) on a per-port basis.

Exceeded Max Hops BPDUs

Times that a BPDU packet is received from a bridge internal to the MST region with a CIST Remaining Hops value less than or equal to 1. This may occur if the receiving bridge is located too far from the CIST regional root bridge (beyond the configured size of the MST region on the CIST regional root bridge) or if a BPDU packet with invalid CIST regional root bridge information is continuously circulating between bridges in the MST Region and needs to be aged out.

This counter is maintained by the CIST (default MST instance 0 in the region) on a per-port basis.

Exceeded Max Hops MSTI MSGs

Times that an MSTI MSG packet is received from a bridge internal to the MST region with an MSTI Remaining Hops value less than or equal to 1. This may occur if the receiving bridge is located too far from the MSTI regional root bridge (beyond the configured size of the MST region on the MSTI regional root bridge) or if a BPDU packet with invalid MSTI regional root bridge information is continuously circulating between bridges in an MST region and needs to be aged out.

This counter is maintained on a per-MSTI per-port basis.

Topology Changes Detected

Times that a Topology Change event is detected by the CIST or MSTI port and the port triggers a topology change propagation throughout the network. A Topology Change event occurs when a non-edge port enters forwarding state.

This counter is maintained on a per-CIST per-port and on a per-MSTI per-port basis.

Topology Changes Tx

Times that Topology Change information is propagated (sent out) through the port to the rest of the network.For a CIST port, the counter is the number of times that a CFG, RST, or MST BPDU with the TC flag set is transmitted out of the port.For an MSTI port, the counter is the number of times that an MSTI configuration message with the TC flag set is transmitted out of the port.

This counter is maintained on a per-CIST per-port and on a per-MSTI per-port bases.

Topology Changes Rx

Times that Topology Change information is received from the peer port.For a CIST port, the counter is the number of times that a CFG, RST, or MST BPDU with the TC flag set is received.For an MSTI port, the counter is the number of times that an MSTI configuration message with the TC flag set is received.

This counter is maintained on a per-CIST per-port and on a per-MSTI per-port basis.

Topology Change ACKs Tx

Times that the Topology Change acknowledgement is transmitted through the port (number of CFG, RST or MST BPDUs transmitted with the Topology Change Acknowledge flag set).

This counter is maintained by the CIST (default MST instance 0) on a per-port basis.

Topology Change ACKs Rx

Times the Topology Change acknowledgement is received on the port (number of CFG, RST or MST BPDUs received with the Topology Change Acknowledge flag set).

This counter is maintained by the CIST (default MST instance 0) on a per-port basis.

TCN BPDUs Tx

Topology Change Notification BPDUs that are transmitted through the port. This counter is maintained by the CIST (default MST instance 0) on a per-port basis.

TCN BPDUs Rx

Topology Change Notification BPDUs that are received on the port.

This counter is maintained by the CIST (default MST instance 0) on a per-port basis.

CFG BPDUs Tx

802.1D Configuration BPDUs that are transmitted through the port.

This counter is maintained by the CIST (default MST instance 0) on a per-port basis.

CFG BPDUs Rx

802.1D Configuration BPDUs that are received on the port.

This counter maintained by the CIST (default MST instance 0) on a per-port basis.

RST BPDUs Tx

802.1w RST BPDUs that are transmitted through the port.

This counter is maintained by the CIST (default MST instance 0) on a per-port basis.

RST BPDUs Rx

802.1w RST BPDUs that are received on the port.

This counter is maintained by the CIST (default MST instance 0) on a per-port basis.

MST BPDUs Tx

802.1s MST BPDUs that are transmitted through the port.

This counter is maintained by the CIST (default MST instance 0) on a per-port basis.

MST BPDUs Rx

802.1s MST BPDUs that are received on the port.

This counter is maintained by the CIST (default MST instance 0) on a per-port basis.

MSTI MSGs Tx

Times that a configuration message for a specific MSTI was encoded in (802.1s) MST BPDUs that are transmitted through the port.

This counter is maintained on a per-MSTI per-port basis.

MSTI MSGs Rx

Times that the MSTI detected a configuration message destined to the MSTI in (802.1s) MST BPDUs received on the port.

This counter is maintained on a per-MSTI per-port basis.