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Ethernet switches have a learning process through which they gradually begin to understand the network topology -- which MAC address is behind which port. When seeing a port to send a frame with a certain source MAC address, the MAC address table is updated to indicate that the source MAC is behind the port that sent the packet.

Now, when moving a computer to another switch port, it typically after a while sends a frame that teaches the entire network its new location in the network. So, the network will eventually learn the new location of the computer.

My question is: do typical Ethernet switches have in addition to this MAC address re-learning a timeout for the MAC address entries in the table? This would be similar to the ARP table timeout in endpoint hosts. If so, what is the range of typical default values for MAC address timeout?

  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 16 '17 at 23:03
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Typical timeout is 5 min. Re-learn MAC can be dangerous in terms of security. On the other hand, if port is goes down when you disconnect your computer from the switch, all MACs associated with the port are flushed immediately and your switch can learn it again from different port. Please be aware that it is a typical behavior and there are some switches configured to stick with a MAC once it was learnt (or to limit number of MACs that can be ever dynamically learnt, once limit reached manual intervention required).

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