10-29
Bridging—Transmitting Non-IP Traffic or Merging Two Networks
Troubleshooting Spanning Tree
Relatively slow convergence with RSTP may be caused by incorrectly config-
ured point-to-point interfaces. View the status for each bridged interface and
make sure that it is using full duplex. The router should automatically assign
it the point-to-point role. If necessary, force this role by entering this command
in the logical interface configuration mode context:
ProCurve(config-fr 1.1)# spanning-tree link-type point-to-point
Incorrect Path Selection
Devices may choose paths that seem illogical for several reasons:
■ an end device or rogue device has been elected root
■ connections are configured with an inappropriate cost
■ a guard or filter has been applied to an interface
When an interface connects to an end device, enable the BPDU guard so that
the router refuses BPDUs from it. Otherwise, software running on the device
may cause it to be elected root. (You can view what device has actually been
elected root with the show spanning-tree command.)
The router selects the primary connection according to which connection
provides the lowest-cost link to the root. The show spanning-tree command
displays which interfaces are active (status = FWD). You can force the router
to select a specific connection by lowering its cost.
You can also assign two equivalent connections the same cost, but still have
the router choose one as primary and one as redundant. Simply lower the port
priority for the primary connection. (See “Determining Which Links Are
Chosen: Setting Link Cost” on page 10-18.) Again, the show spanning-tree
command displays the cost and priority for each interface in the bridge.
If an interface is not participating in the spanning tree, check the running-
config for guards or filters that may have been inadvertently assigned to it.
Also view the global spanning tree configuration and make sure that the global
BPDU guard and/or filter has not been applied.
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