350-401 Question 170

Community Discussion

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• Chose AC1

  Bridge priority must be multiples of 4096 (default is 32,768) The bridge with the lowest priority value becomes the root bridge. Option 'A' ensures that DSW1 is selected as the "root" bridge. Option 'C' also ensures that switch "DSW1" is the root bridge by modifying DSW2 priority. We can use either of these 2 methods to influence the root bridge selection. Option B uses the wrong syntax, it should be "DSW1(config)#spanning-tree vlan 10 root" Option D is incorrect, port priority is configured under the interface settings "DSW1(config-if)# spanning-tree VLAN 10 port-priority 0" which is used to influence root port selection in non-root bridges. Option E ensures DSW2 is the root for VLAN 20 which doesn't match our requirement.

• 1

  In option B, you must specify that the root is primary (we have primary and secondary roots). "DSW1(config)#spanning-tree vlan 10 root primary" With this command, DSW1 will look for the primary root, which is DSW2 in our case. It will check DSW2’s priority of 24,576 and set its own priority to a lower multiple of 4,096, which is 20,480. https://www.ciscopress.com/articles/article.asp?p=2995351&seqNum=2#:~:text=You%20can%20modify%20the%20port,VLAN%2Dby%2DVLAN%20basis. https://networklessons.com/spanning-tree/spanning-tree-root-bridge-configuration

• 2

  A. is correct: the lower prio will win B is not correct due to there is missing subcommand after root (primary/secondary) Switch(config)#spanning-tree vlan 10 root ? primary Configure this switch as primary root for this spanning tree secondary Configure switch as secondary root C is correct, if you modifiy DSW2 prio to 61440 DSW1 will have the best prio