Specifications

CHAPTER 3
Spanning Tree
Identifying a Bridging Loop
Suspect a loop if you see the following:
n You capture traffic on a link and see the same frames multiple times.
n All users in a bridging domain have connectivity problems at the same time.
n There is abnormally high port utilization.
To remedy a loop quickly, shut redundant ports and then enable them one at a time. Some switches enable debugging of
STP to help in diagnosing problems. The following commands are useful for isolating a bridging loop:
show interfaces
show spanning tree
show bridge
show process cpu
debug spanning tree
show mac address-table aging-time vlan#
show spanning-tree vlan vlan# detail
Spanning-Tree Best Practices
To optimize data flow in the network, design and configure Spanning Tree in the following ways:
n Statically configure switches to be the primary and secondary root bridges by setting priority values.
n Consider which interfaces will become designated and root ports (possibly set port priorities/path cost).
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CCNP SWITCH 642-813 Quick Reference by Denise Donohue