200-301 · Question #1445
How does MAC learning function?
The correct answer is A. enabled by default on all VLANs and interfaces. MAC learning is a fundamental function of an Ethernet switch, automatically building a MAC address table by observing source MAC addresses of incoming frames to efficiently forward traffic.
Question
How does MAC learning function?
Options
- Aenabled by default on all VLANs and interfaces
- Bincreases security on the management VLAN
- Csends frames with unknown destinations to a multicast group
- Dinspects and drops frames from unknown destinations
How the community answered
(25 responses)- A96% (24)
- C4% (1)
Why each option
MAC learning is a fundamental function of an Ethernet switch, automatically building a MAC address table by observing source MAC addresses of incoming frames to efficiently forward traffic.
Ethernet switches use MAC learning to dynamically build their MAC address tables by examining the source MAC addresses of frames received on each port. This process is active by default on all operational VLANs and interfaces to enable proper frame forwarding.
While MAC learning is crucial for switch operation, specific security features like port security or 802.1X are used to increase security on VLANs, not MAC learning itself.
Frames with unknown *unicast* destination MAC addresses are typically flooded out all ports within the VLAN (except the ingress port), not sent to a multicast group.
MAC learning's primary function is to build the forwarding table; frames with unknown destinations are usually flooded, not dropped, unless specific port security or other security policies are configured.
Concept tested: Ethernet MAC address learning
Source: https://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/23689-mac-address-table.html
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