Configuring the WSM using Device Manager

Why multiple Spanning Trees?

The figure below shows a simple example of multiple spanning trees. Two VLANs, VLAN 1 and VLAN 100 exist between WSM A and WSM B. If VLAN 1 and VLAN 100 are in the same Spanning Tree topology or Spanning Tree Group, then a loop exists between the two WSMs. If one of the ports is blocked, then the VLAN loses connectivity between the WSMs. If VLAN 1 and VLAN 100 belong to different Spanning Tree Groups, then the two instances of Spanning Tree separate the topology without forming a loop. Both VLANs can forward packets between WSMs without losing connectivity.

See also:

• About Spanning Tree protocol
• VLANs and spanning tree protocol
• Understanding multiple spanning trees
• Root cost comparison
• Example--four-WSM topology with single spanning tree
• Example--four-WSM topology with multiple spanning trees
• Multiple spanning tree example--determining root cost
• Configuring spanning tree protocol