Displaying the change history of root bridges
Syntax:
show spanning-tree root-history vlan <vlan-id>
Displays the last 10 root bridge changes on a specified VLAN configured with RPVST+. Included are the timestamp and Root Bridge ID recorded at each root bridge change.
Use the
show spanning-tree root-history
command to view the number and dates of changes in the assignment of a root bridge. Possible intrusion into your VLAN network may occur if an unauthorized external device gains access to a spanning tree by posing as the root device in a topology. To prevent a port connected to the device from being selected as the root port in a topology, use the
spanning-tree root-guard
command.
Displaying the change history of root bridges
switch# show spanning-tree root-history vlan 20 Status and Counters - RPVST Root Changes History VLAN ID : 20 Root Changes Counter : 53 Current Root Bridge ID : 32768:0024a8-d13a40 Root Bridge ID Date Time ------------------- ---------- -------- 32768:0024a8-d13a40 05/04/2012 21:54:11 0:001185-c6e500 05/04/2012 21:54:07 32768:0024a8-d13a40 05/04/2012 16:41:11 0:001185-c6e500 05/04/2012 16:41:11