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Multiple Instance Spanning-Tree Operation
Troubleshooting an MSTP Configuration
Troubleshooting MSTP Operation
Table 3-2. Troubleshooting MSTP Operation
RST BPDUs Tx Number of (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 Number of (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 Number of (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 Number of (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 Number of 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 Number of 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.
Field Description
Problem Possible Cause
Duplicate packets on a VLAN, or packets not
arriving on a LAN at all.
The allocation of VLANs to MSTIs may not be identical among all
switches in a region.
A switch intended to operate in a region does
not receive traffic from other switches in the
region.
An MSTP switch intended for a particular region may not have the same
configuration name or region revision number as the other switches
intended for the same region. The MSTP configuration name (spanning-
tree config-name command) and MSTP configuration revision number
(spanning-tree config-revision command) must be identical on all MSTP
switches intended for the same region.
Another possible cause is that the set of VLANs and VLAN ID-to-MSTI
mappings (spanning-tree instance vlan command) configured on the
switch may not match the set of VLANs and VLAN ID-to-MSTI mappings
configured on other switches in the intended region.
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