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Friday, April 23, 2010

L2 switch. Does the MAC entry table age out the MAC-address after the 600 seconds default?


We have a PC connected to a L2 Switch. We see the MAC address as dynamic in the switch's MAC-Address table. As soon as we disconnect the PC from the switch the entry in the MAC-Table is gone..... doesn't it suppose to age out the MAC-address after the 600 seconds default and not right away? Can someone confirm?


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.

If the PCs are running Microsoft IE 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.

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