Spanning-Tree Root-Bridge Election | 200-125 Cisco Exam

Understanding the Spanning-Tree Root-Bridge Election Process

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Which statement about spanning-tree root-bridge election is true?



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A. B. C. D.


Spanning Tree Protocol (STP) is a Layer 2 protocol that prevents switching loops by managing the forwarding path of data frames in a redundant switched network. STP elects a root bridge, which is the reference point for all other switches in the network, and determines the path for each VLAN.

Regarding the statement about spanning-tree root-bridge election, the correct answer is D. Each VLAN must have its own root bridge. This means that each VLAN can have a different root bridge, and the root bridge for one VLAN may not be the root bridge for another VLAN.

The root bridge is the switch with the lowest bridge ID in the network, which is determined by the priority value and the MAC address of the switch. By default, the priority value is 32,768, and the MAC address is used to break any ties.

When STP is enabled on a switch, it sends out Bridge Protocol Data Units (BPDUs) to other switches in the network to determine the best path to the root bridge. The switch with the lowest path cost to the root bridge becomes the designated switch for that segment, and all traffic for that segment is forwarded to the root bridge.

In a multi-VLAN network, each VLAN can have its own root bridge, which can improve network performance by allowing traffic to take the shortest path to the root bridge for that VLAN. By default, all VLANs use the same root bridge, but this can be changed by adjusting the priority value for each VLAN.

In conclusion, the statement "Each VLAN must have its own root bridge" is true in a multi-VLAN network, where each VLAN can have its own root bridge to improve network performance.