if no bridge priority is configured in pvst, which criteria is considered when electing the root bridge?

June 28, 2026

If no bridge priority is configured in PVST, the root bridge is elected based on the lowest MAC address among the switches.

How the election works (quick view)

Every switch has a Bridge ID (BID) that consists of:
- Bridge priority (default 32768 if you don’t configure it).

* The switch’s MAC address.

If you do not change the priority, all switches share the same default priority value.

With identical priorities, the tie-breaker for the root bridge election becomes the lowest MAC address , so the switch with the smallest MAC wins and becomes the root bridge.

Common exam-style answer

When the question is framed like:

If no bridge priority is configured in PVST, which criteria is considered when electing the root bridge?
a. Lowest MAC address
b. Highest IP address
c. Lowest IP address
d. Highest MAC address

The correct choice is: a. Lowest MAC address.

Mini HTML table for quick memorization

html

<table>
  <tr>
    <th>Condition</th>
    <th>Root bridge decision</th>
  </tr>
  <tr>
    <td>Custom priorities configured</td>
    <td>Lowest bridge priority wins; if tied, lowest MAC address. [web:1][web:3][web:9]</td>
  </tr>
  <tr>
    <td>No priority configured (default on all)</td>
    <td>All priorities equal → root is switch with lowest MAC address. [web:1][web:3][web:5][web:7]</td>
  </tr>
</table>

TL;DR: In PVST, if you leave priorities at default, the switch with the lowest MAC address becomes the root bridge.

Information gathered from public forums or data available on the internet and portrayed here.