200-301 · Question #1361
How does MAC learning function on a switch?
The correct answer is A. associates the MAC address with the port on which it is received. MAC learning on a switch builds a forwarding table by associating the source MAC address of incoming frames with the port they were received on.
Question
Options
- Aassociates the MAC address with the port on which it is received
- Brewrites the source and destination MAC address
- Cbroadcasts frames to all ports without queueing
- Dsends an ARP request to locate unknown destinations
How the community answered
(26 responses)- A92% (24)
- C4% (1)
- D4% (1)
Why each option
MAC learning on a switch builds a forwarding table by associating the source MAC address of incoming frames with the port they were received on.
A switch learns MAC addresses by examining the source MAC address of frames entering its ports and then associating that MAC address with the specific port through which the frame was received. This information is stored in the MAC address table (CAM table) for efficient future forwarding decisions.
Switches forward frames based on MAC addresses; they do not rewrite the source and destination MAC addresses, which is typically a function of NAT or routing on Layer 3 devices.
Broadcasting frames to all ports without queueing is not the primary function of MAC learning; switches broadcast only for unknown unicast, broadcast, and multicast traffic, and frames are always queued.
Sending an ARP request is a Layer 3 function used to resolve an IP address to a MAC address, not a mechanism for a switch to learn MAC addresses.
Concept tested: Switch MAC Address Learning
Source: https://www.cisco.com/c/en/us/support/docs/lan-switching/ethernet-switching/10574-5.html
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