200-101 Question #1: Real Exam Question with Answer & Explanation

The correct answer is D: It has a higher bridge ID than the elected root bridge.. The root bridge is elected based on the lowest Bridge ID. A Bridge ID is composed of a 2-byte bridge priority (default 32768) plus the switch's MAC address. If this switch has a higher Bridge ID than another switch in the network - either due to a higher priority value or a highe

Question

Refer to the exhibit.
Why has this switch not been elected the root bridge for VLAN1?

Options

AIt has more than one interface that is connected to the root network segment.
BIt is running RSTP while the elected root bridge is running 802.1D spanning tree.
CIt has a higher MAC address than the elected root bridge.
DIt has a higher bridge ID than the elected root bridge.

Explanation

The root bridge is elected based on the lowest Bridge ID. A Bridge ID is composed of a 2-byte bridge priority (default 32768) plus the switch's MAC address. If this switch has a higher Bridge ID than another switch in the network - either due to a higher priority value or a higher MAC address - it will not be elected root bridge. Answer D is correct because the fundamental rule is: the switch with the lowest Bridge ID wins the root bridge election. Answer C is partially related but incomplete - it's the combined Bridge ID (priority + MAC) that matters, not the MAC address alone. RSTP compatibility (B) does not prevent root bridge election, and having multiple interfaces on a segment (A) is irrelevant to root bridge election.

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