200-301 · Question #963
What happens when a switch receives a frame with a destination MAC address that recently aged out?
The correct answer is B. The switch floods the frame to all ports in the VLAN except the port that received the frame.. When a switch receives a frame for which the destination MAC address has aged out of its MAC address table, the switch treats it as an unknown unicast and floods it within the same VLAN. This ensures the frame reaches its intended recipient if it is still active, while the switch
Question
Options
- AThe switch floods the frame to all ports in all VLANs except the port that received the frame.
- BThe switch floods the frame to all ports in the VLAN except the port that received the frame.
- CThe switch references the MAC address aging table for historical addresses on the port that
- DThe switch drops the frame and learns the destination MAC address again from the port that
How the community answered
(31 responses)- A10% (3)
- B84% (26)
- C3% (1)
- D3% (1)
Why each option
When a switch receives a frame for which the destination MAC address has aged out of its MAC address table, the switch treats it as an unknown unicast and floods it within the same VLAN. This ensures the frame reaches its intended recipient if it is still active, while the switch attempts to relearn the MAC address.
Flooding occurs only within the VLAN where the frame was received, not across all VLANs.
When a switch receives a frame with a destination MAC address that is no longer in its MAC address table (due to aging out), it treats the frame as an unknown unicast. To ensure delivery, the switch floods the frame out all ports in the same VLAN, excluding the ingress port, hoping the destination will respond and allow the switch to relearn its MAC address.
The switch does not reference historical addresses; if an entry has aged out, it's considered unknown.
The switch does not drop the frame; instead, it floods it to attempt delivery and relearn the address.
Concept tested: Switch MAC address aging and flooding
Source: https://learningnetwork.cisco.com/s/article/cisco-switch-mac-address-table-aging-and-unknown-unicast-flooding
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