| 5.3 | VLANs and STP | ||
| 5.3.2 | Common STP |
| The IEEE 802.1Q standard uses an
approach to VLANs referred to as mono or common Spanning Tree. The
STP runs on VLAN 1, which is the default VLAN. All switches elect a
single root bridge and form an association with that root bridge.
In the Figure, a single root bridge
has been elected for the red and green VLANs. Notice that the root
bridge is optimized for the red VLAN, but some of the green VLAN
users must take a less-than-optimal path to get to their file
servers. A CST approach does not allow for optimization of the
root-bridge placement per VLAN.
CST disadvantages are as follows:
|