Last Updated on August 1, 2021 by Admin 2
You have three switches connected as shown in the diagram below: S1, S2, and S3.
You instructed your assistant to configure the switches so that the following requirements would be met:
Switch 1 should be the root bridge for VLAN A
VLAN C should forward over the Gig 1/0/1 link between Switch 2 and Switch 3
VLAN B should forward over the Gig 1/0/2 link between Switch 2 and Switch 3However, after your assistant performs the configuration, you discover that:
Switch 2 is the root bridge for VLAN A
VLAN C is forwarding over the Gig 1/0/2 link between Switch 2 and Switch 3
VLAN B is forwarding over the Gig 1/0/1 link between Switch 2 and Switch 3When you execute the show spanning tree command on Switch 2, you determine that all link costs and priorities are set at the defaults.Which of the following actions performed on Switch 2 would enable the desired configuration? (Choose three. Each correct answer is part of one solution.)
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switch2(config)# spanning-tree vlan a priority 61440 -
switch2(config)# spanning-tree vlan a priority 1
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switch2(config)# int G1/0/2switch2(config-if)# spanning-tree vlan b cost 1 -
switch2(config)# int G1/0/2switch2(config-if)# spanning-tree vlan b cost 19
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switch2(config)# int G1/0/1switch2(config-if)# spanning-tree vlan c port-priority 64 -
switch2(config)# int G1/0/1switch2(config-if)# spanning-tree vlan c port-priority 128
The commands that will achieve the desired results are:
switch2(config)# spanning-tree vlan a priority 61440 switch2(config)# interface G1/0/2 switch2(config-if)# spanning-tree vlan b cost 1 switch2(config)# interface G1/0/1 switch2(config-if)# spanning-tree vlan c port-priority 64
The first command raises the bridge priority for Switch 2 with respect to VLAN A, which will cause Switch 1 to be the root bridge for VLAN A. By default, the bridge priorities for Switch 2 and Switch 3 will set to 32769.
The second command will lower the cost of G1/0/2 with respect to VLAN B. Since the cost for G1/0/1 is the default cost of 4, this will cause interface G1/0/2 to become the root port for VLAN B, which will in turn cause it to forward instead of block for VLAN B.
The third command will lower the port priority for G1/0/1 with respect to VLAN C. Since the port priority of G1/0/2 will remain set at the default of 128, this will result in switching the ports that are blocking and forwarding. The end result will be that VLAN C will start forwarding over the Gig 1/0/1 link between Switch 2 and Switch 3.
The other commands will have no effect because they change the cost and port priority to the defaults, which are how the links are currently set.
Objective:
Layer 2 Technologies
Sub-Objective:
Configure and verify spanning tree