Interface Blocking State - Characteristics | JN0-360 Exam - Juniper Networks

Interface Blocking State

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Question

What are two characteristics of an interface that has been placed in the blocking state by STP? (Choose two.)

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A. B. C. D.

AB

The Spanning Tree Protocol (STP) is a network protocol that helps prevent loops in Ethernet networks by dynamically blocking redundant paths. When STP detects redundant paths, it selects one path as the primary and blocks the others. The blocked paths are placed in the blocking state, also known as the discarding state. When a port is in the blocking state, it is not forwarding frames.

Therefore, the two characteristics of an interface that has been placed in the blocking state by STP are:

B. It listens to received BPDUs - When a port is in the blocking state, it continues to receive BPDUs (Bridge Protocol Data Units) from other switches. These BPDUs help the switch determine the network topology and update its STP state accordingly. The switch continues to listen to BPDUs to ensure that it does not create any loops or forwarding loops in the network.

A. It drops all data frames - When a port is in the blocking state, it does not forward any data frames. Instead, it discards all incoming frames. This prevents the switch from forwarding frames over a redundant path and causing a loop. The switch will only forward frames when it has selected a new path that is not blocked.

C. It is worth noting that the statement "It uses learned MAC addresses to populate the MAC table" is not true for an interface in the blocking state. The switch does not use MAC addresses from frames received on a blocked port to populate the MAC table. The switch only learns MAC addresses from frames received on non-blocking ports.