Quick Reference Guide

160 | Spanning Tree
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Figure 10-120 displays the output from the show spanning-tree mst port summary command for STP details
of individual ports:
Figure 10-120. Example Output of show spanning-tree mst port summary Command
The selection of 1/0/1 as the root port was based, in this case, on the value of the assigned cost. As shown
by the use of the
show spanning-tree mst port detailed command in Figure 10-121, the cost through
1/0/1 is 0 (zero), because it is directly connected to a designated port on the root bridge, and it is receiving
a 0 cost value to the root bridge. 1/0/2 is receiving a cost of 20000 to the root from its connection to 1/0/2
of S50-3. So the shorter route to the root is through 1/0/1.
Figure 10-121. Example Output from show spanning-tree mst port detailed Command for
Individual Ports
S50-2 #show spanning-tree mst port summary 0 1/0/1
MST Instance ID................................ CST
STP STP Port
Interface Mode Type State Role
--------- -------- ------- ----------------- ----------
1/0/1 Enabled Forwarding Root
S50-2 #show spanning-tree mst port summary 0 1/0/2
MST Instance ID................................ CST
STP STP Port
Interface Mode Type State Role
--------- -------- ------- ----------------- ----------
1/0/2 Enabled Forwarding Designated
S50-2 #show spanning-tree mst port detailed 0 1/0/1
Designated Port Cost........................... 0
S50-2 #show spanning-tree mst port detailed 0 1/0/2
Designated Port Cost........................... 20000