Which IEEE standard prevents Layer 2 loops by logically blocking redundant paths?

Which IEEE standard prevents Layer 2 loops by logically blocking redundant paths?

• A. RSTP
• B. LACP
• C. MSTP
• D. STP

Answer: (D)

The main idea is to prevent Layer 2 loops by creating a single, loop-free path through the network and blocking any redundant ones. The Spanning Tree Protocol (IEEE 802.1D) does this by electing a root bridge and calculating the best path to the root for every switch. On each network segment, one port is chosen to forward frames (the designated port) while other redundant ports are placed in a blocking state. This logical blocking of extra paths ensures there’s only one active path between any two devices, so frames don’t loop endlessly. Other options either modify how this loop-free state is achieved or serve a different purpose. Rapid Spanning Tree Protocol (IEEE 802.1W) still blocks redundant paths to prevent loops but converges faster after changes. Multiple Spanning Tree Protocol (IEEE 802.1S) extends the concept to allow different spanning trees for different VLANs. Link Aggregation Control Protocol (often associated with IEEE 802.1ad/802.3ad) bundles multiple physical links into a single logical link for bandwidth and redundancy, but it doesn’t by itself prevent loops at Layer 2.

The main idea is to prevent Layer 2 loops by creating a single, loop-free path through the network and blocking any redundant ones. The Spanning Tree Protocol (IEEE 802.1D) does this by electing a root bridge and calculating the best path to the root for every switch. On each network segment, one port is chosen to forward frames (the designated port) while other redundant ports are placed in a blocking state. This logical blocking of extra paths ensures there’s only one active path between any two devices, so frames don’t loop endlessly.

Other options either modify how this loop-free state is achieved or serve a different purpose. Rapid Spanning Tree Protocol (IEEE 802.1W) still blocks redundant paths to prevent loops but converges faster after changes. Multiple Spanning Tree Protocol (IEEE 802.1S) extends the concept to allow different spanning trees for different VLANs. Link Aggregation Control Protocol (often associated with IEEE 802.1ad/802.3ad) bundles multiple physical links into a single logical link for bandwidth and redundancy, but it doesn’t by itself prevent loops at Layer 2.