Switches and Root Bridge in Cisco Networks

# Which Switch Takes Over When the Primary Root Bridge Fails?

### Question

If all switches are configured with default values, which switch will take over when the primary root bridge experiences a power loss?

### Explanations

Click on the arrows to vote for the correct answer

A. B. C. D.

C

When a network consists of multiple switches, a hierarchical structure is established with a root bridge at the top. The root bridge is responsible for controlling the flow of traffic and ensuring that there are no loops in the network topology.

In the event that the primary root bridge experiences a power loss, one of the other switches in the network will take over as the root bridge. This is determined by the Bridge ID, which is a combination of the Bridge Priority and the MAC address of the switch. The switch with the lowest Bridge ID will become the new root bridge.

In this scenario, since all switches are configured with default values, the Bridge Priority of all switches is set to the default value of 32768. The MAC addresses of the switches are:

• switch 00E0.F90B 6BE3
• switch 0004.9A1A C182
• switch 0040.0BC0 90C5
• switch 00E0.F726 3DC6

To determine which switch will become the new root bridge, we need to calculate the Bridge ID for each switch. This is done by adding the Bridge Priority and the MAC address together.

The Bridge ID for each switch is:

• switch 00E0.F90B 6BE3: 32768 + 00E0.F90B.6BE3 = 32768.00E0.F90B.6BE3
• switch 0004.9A1A C182: 32768 + 0004.9A1A.C182 = 32768.0004.9A1A.C182
• switch 0040.0BC0 90C5: 32768 + 0040.0BC0.90C5 = 32768.0040.0BC0.90C5
• switch 00E0.F726 3DC6: 32768 + 00E0.F726.3DC6 = 32768.00E0.F726.3DC6

The switch with the lowest Bridge ID is switch 0004.9A1A C182, so it will become the new root bridge if the primary root bridge experiences a power loss. Therefore, the correct answer is C. switch 0004.9A1A C182.