Cisco Catalysts - MAC address pool

Unanswered Question
Oct 30th, 2007

Hi all,


I have a question regarding the number of MAC addresses available to Catalysts switches. For example if turn all 24 FastEthernet ports on a 3750 to layer 3 ports with unique IP addresses - does the switch utilize 24 unique MACs?


Or even more extreme - a 6513 with several 48 port blades - all layer 3 ports. Would the switch take on separate MACs for each interface?


Could you hit a limit and run out?


Many thanks,


Paul


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Collin Clark Tue, 10/30/2007 - 09:09

Yes each interface has a MAC, but so does each device connected to each port. Each trunk port has all the L2 downstream MACs! As you can image that can add up to a lot. And yes switches have a limit to the number of MACs they can have in their table. Check out a switches datasheet for that number. Remember though that the MAC table purges each MAC addresses based on time and so you would never see all the MAC addresses in the table.


HTH and please rate.

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