CAM - aging time?

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Apr 21st, 2010
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I have a PC connected to a L2 Switch. I see the MAC address as dynamic in the switch's MAC-Address table. As soon as I disconnect the PC from the switch the entry in the MAC-Table is gone..... doesn't it supppose to age out the MAC-address after the 600 seconds default and not right away? I'm I missunderstanding the concept? Please help.

Correct Answer by Jon Marshall about 7 years 1 week ago

fjcardenas-1 wrote:


Thank you for your answer John. I set the aging time to 60 seconds. I have the PC connected to the switch and after several minutes I still see the MAC address in the MAC-Address table. I am not doing anything in the PC (browsing, mail, etc. unless there is an undergroung process but doubt it). I just want to test how the aging thing work.


That's the problem with modern PCs especially if they are running Microsoft ie. you don't really have to be doing anything as they are often continually chatting away in the background. If you staryed a network sniffer up on your PC you would see there is often still traffic going back and forth.


Jon

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Jon Marshall Wed, 04/21/2010 - 13:01
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The CAM aging time is used when the device is still connected to the switchport but hasn't actually sent or received any traffic for a certain time. If the device hasn't sent or received any data within the aging time the entry is removed and is only added when the device sends or receives traffic again.


When you disconnect the PC however the switch automatically removes the mac-address of the PC associated with the port because it knows the switchport has nothing connected to it so there can be mac-address reachable on that port.


Jon

fjcardenas-1 Wed, 04/21/2010 - 13:16
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Thank you for your answer John. I set the aging time to 60 seconds. I have the PC connected to the switch and after several minutes I still see the MAC address in the MAC-Address table. I am not doing anything in the PC (browsing, mail, etc. unless there is an undergroung process but doubt it). I just want to test how the aging thing work.

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Jon Marshall Wed, 04/21/2010 - 13:20
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fjcardenas-1 wrote:


Thank you for your answer John. I set the aging time to 60 seconds. I have the PC connected to the switch and after several minutes I still see the MAC address in the MAC-Address table. I am not doing anything in the PC (browsing, mail, etc. unless there is an undergroung process but doubt it). I just want to test how the aging thing work.


That's the problem with modern PCs especially if they are running Microsoft ie. you don't really have to be doing anything as they are often continually chatting away in the background. If you staryed a network sniffer up on your PC you would see there is often still traffic going back and forth.


Jon

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