Blocking State

Definition

Blocking is the STP state where a port does not forward user traffic. It only listens for STP BPDUs to monitor the network.

The Problem That Led to It

Redundant links are useful for backup, but if all links forward traffic, loops occur.

What Problem It Solves

It prevents network loops while keeping the backup link available if the active path fails.

What Happens If Not Used

Loops, broadcast storms, and unstable networks.

Easy Wording

The road is closed, but it's ready to open if needed.

Layman Example

A backup road is closed until the main road becomes unavailable.

Technical Example

Before: Two parallel links forward traffic.

After: STP blocks one link, leaving it as a backup.

Limitation

If the network changes, the blocked port cannot start forwarding immediately.

Solution

The port enters Listening State before forwarding.