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Refer to the following partial output of the show spanning-tree command.
Which of the following statements are TRUE for the given output? (Choose all that apply.)
A. SW1 is the root bridge for VLAN0001
B. Fa0/2 is the root port for VLAN0001
C. The switch having the 0A61.0015.4D02 bridge ID is the root bridge for VLAN0001
D. The switch having the 0F2C.08A1.330E bridge ID is the root bridge for VLAN0001
E. The switch connected to the Fa0/6 port of SW1 is using its root port
F. The port Fa0/4 is in a blocking state for VLAN 0121
G. The STP protocol in use is RSTP
Correct Answer: BCE
Explanation/Reference:
Answer:
The following statements are correct about the given output:
Fa0/2 is the root port for VLAN001
The switch having the 0A61.0015.4D02 bridge ID is the root bridge for VLAN0001
The switch connected to the Fa0/6 port of SW1 is using its root port
The value in the Role column in the output for VLAN0001 is Root for the Fa0/2 port of SW1. This implies that the Fa0/2 port is a root port. A root port is the port on a non-root bridge that has the least cost to reach the root bridge. Every nonroot bridge must elect a root port. A root bridge does not have any root ports.
The output for VLAN0121 specifies Desg in the Role column for the Fa0/6 port of SW1. This implies that the Fa0/6 port is a designated port. This means that the switch on the other end is using its root port.
The switch having the 0A61.0015.4D02 bridge ID is the root bridge for VLAN0001. For VLAN0001, the bridge ID of the root and the local switch are different. The bridge ID of the local switch (SW1) is 0F2C.08A1.330E, while the bridge ID of the root bridge is 0A61.0015.4D02. The text Port 1 (FastEthernet0/2) in the Root ID section for VLAN0001 in the output indicates that the root bridge is connected to the Fa0/2 port of the local switch.
The options stating that SW1 is the root bridge for VLAN0001 and that the switch having the 0F2C.08A1.330E bridge ID is the root bridge for VLAN0001 are incorrect. The Bridge ID section in the output for VLAN0001 and VLAN0121 specifies the bridge ID of the local switch. In this case, the bridge ID of the local switch (SW1) is 0F2C.08A1.330E. SW1 is not the root bridge for VLAN001; however, SW1 is the root bridge for VLAN0121.
You can determine if a local switch is the root bridge by any of the following:
The text This bridge is the root appears in the Root ID section of the output for VLAN0121.
The bridge IDs in the Root ID and Bridge ID sections of the output are the same.
All the ports of the local switch are Desg (designated) ports and in forwarding state.
The port Fa0/4 is NOT in a blocking state for VLAN 0121. As indicated in the STS column for Fa0/4 under the section on VLAN 0121, it states that is in an a FWD (forwarding) state.
The STP protocol in use is NOT Rapid Spanning Tree protocol (RSTP). If that were the case, the output would display Spanning tree enabled protocol rstp, rather than Spanning tree enabled protocol ieee. This indicates that IEEE 802.1d is in use.
Objective:
Layer 2 Technologies Sub-Objective:
Configure and verify spanning tree
References:
Cisco Press > Articles > Network Technology > General Networking > CCNP Exam Prep: Traditional Spanning Tree Protocol Cisco > Cisco IOS Bridging Command Reference > show spanning-tree
Correct Answer: BD and maybe E if fa0 / 4 is not on the same switch.
Sorry!
Correct Answer: BC and maybe E if fa0 / 4 is not on the same switch as fa0 / 6.