Homework Help: Questions and Answers: Which address is used by a Layer 2 switch to build its MAC address table?
A. Broadcast address
B. Source IP address
C. Destination IP address
D. Source MAC address
E. Destination MAC address
Answer:
First, let’s understand what Layer 2 (Data Link Layer) is:
- Layer 2 in the OSI model is the Data Link Layer, which deals with MAC (Media Access Control) addresses.
- A Layer 2 switch operates at this level, forwarding frames based on MAC addresses.
MAC Address Table:
- The MAC address table (also called the CAM table) is a table that a switch uses to associate MAC addresses with the physical ports on the switch.
- This table allows the switch to know where to forward frames so they reach the correct destination.
How the MAC Address Table is Built:
- When a switch receives a frame on one of its ports, it inspects the Source MAC address of the frame.
- The switch adds this Source MAC address to its MAC address table, mapping it to the port on which the frame was received.
- This way, the switch learns which devices are connected to which ports.
Given Options: Step by Step Answering
a) Broadcast address
- The broadcast address is used to send a frame to all devices on a network. It is not used by the switch to build its MAC address table.
b) Source IP address
- The IP address operates at Layer 3 (Network Layer) and is not relevant to a Layer 2 switch’s MAC address table.
c) Destination IP address
- Similar to the source IP address, the destination IP address is Layer 3 information, not used by a Layer 2 switch.
d) Source MAC address
- This is the address that the switch uses to learn which devices are connected to which ports. The switch records this address in its MAC address table.
e) Destination MAC address
- The switch looks at the destination MAC address to decide where to forward the frame but does not use it to build the MAC address table.
Final Answer
Based on the above analysis, the correct answer is:
D. Source MAC address.
The Layer 2 switch uses the Source MAC address to build and update its MAC address table. Therefore, the correct answer is D. Source MAC address.
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