Why has this switch not been elected the root bridge for VLAN1?

Topic 2, LAN Switching Technologies

Refer to the exhibit.

Why has this switch not been elected the root bridge for VLAN1?
A . It has more than one interface that is connected to the root network segment.
B . It is running RSTP while the elected root bridge is running 802.1d spanning tree.
C . It has a higher MAC address than the elected root bridge.
D . It has a higher bridge ID than the elected root bridge.

View Answer

Answer: D

Explanation:

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a008009482f.shtml

When a switch receives a BPDU, it first compares priority, the lower number wins. If a tie, compare MAC, the smaller one wins. Here Switch has 32769 priority which is greater than 20481 so switch will not elect for root bridge. It says the bridge priority for Switch is 32769, and the root priority is 20481.

Which means that some other switch has the lower priority and won the election for VLAN 1.