At which OSI layer does STP operate?
A. Physical
B. Network
C. Transport
D. Data Link
Correct Answer: D
Explanation/Reference:
Answer:
Spanning Tree Protocol (STP) operates at the Data Link layer (Layer 2) of the OSI model.
Switches and bridges running the spanning-tree algorithm communicate by exchanging multicast messages called bridge protocol data units (BPDUs) at regular intervals. BPDUs are used to build and maintain the spanning tree, ensuring a stable loop-free topology.
BPDU exchange facilitates the following:
Election of a root switch (only one per spanning tree)
Election of a designated switch for each switched segment
Removal of loops by placing redundant switch ports in a backup (non-forwarding) state
STP is implemented on bridges and switches in order to prevent loops in the network. STP should be used in situations where redundant links are used.
Objective:
Layer 2 Technologies Sub-Objective:
Configure and verify spanning tree
References:
Cisco > Home > Support > Technology Support > LAN Switching > Spanning Tree Protocol > Configure > Configuration Examples and Technotes > Spanning Tree Protocol > Understanding and Configuring Spanning Tree Protocol (STP) on Catalyst Switches
Cisco > Support > Configuring Spanning Tree Protocol > How STP Works
Explanation/Reference:
Answer:
Spanning Tree Protocol (STP) operates at the Data Link layer (Layer 2) of the OSI model.
Switches and bridges running the spanning-tree algorithm communicate by exchanging multicast messages called bridge protocol data units (BPDUs) at regular intervals. BPDUs are used to build and maintain the spanning tree, ensuring a stable loop-free topology.
BPDU exchange facilitates the following:
Election of a root switch (only one per spanning tree)
Election of a designated switch for each switched segment
Removal of loops by placing redundant switch ports in a backup (non-forwarding) state
STP is implemented on bridges and switches in order to prevent loops in the network. STP should be used in situations where redundant links are used.
Objective:
Layer 2 Technologies Sub-Objective:
Configure and verify spanning tree
References:
Cisco > Home > Support > Technology Support > LAN Switching > Spanning Tree Protocol > Configure > Configuration Examples and Technotes > Spanning Tree Protocol > Understanding and Configuring Spanning Tree Protocol (STP) on Catalyst Switches
Cisco > Support > Configuring Spanning Tree Protocol > How STP Works