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This question is regarding in the process of L2 MAC Address learning. As we know, if a sender sends a packet to some receiver host which switch doesn't know, it will broadcast for learning.

Assume an Ethernet frame received at switch, the Target MAC is not exists in the MAC Table(for some reason), the switch broadcast for learning the new MAC.

Can anyone tell here, Is there any time out kind of thing? How long switch will wait for a response?

(Suppose if such MAC never exists, anyway it will drop, but any timeout is there)

Thanks in advance for the response.

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    A switch doesn't broadcast to learn an unknown destination MAC address. If floods the frame out all active ports except the port from which it received the frame. I am pretty sure this is a duplicate question, but I don't have the time at the moment to find it.
    – YLearn
    Aug 26, 2019 at 7:14
  • Besides the above linked question, see this question and answers.
    – Ron Maupin
    Aug 26, 2019 at 14:33

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As we know, if a sender sends a packet to some receiver host which switch doesn't know, it will broadcast for learning.

That's not correct. If a switch hasn't learned the destination MAC of a frame, it'll flood the frame to all ports but the one it was received from, mimicking a repeater hub.

Still, it only learns/updates the source MAC. Only when the destination MAC host sends a frame (with its MAC as source), then the switch learns the MAC.

Generally, a switch processes each frame by itself. It just stores the MAC-port associations in its MAC table and that's it.

Technically, the function and the timeout you're asking about doesn't exist. Practically, it works somewhat like that but that depends on the destination host, not the switch in between.