Examples of Disconnecting and Reconnecting Devices

The following figure shows Device A connected to an Extreme Networks device with MAC lockdown timeout configured for the ports.

sWhen Device A starts sending traffic, the source MAC address is learned on the port, the FDB entry is created, and the MAC lockdown timer is started for the entry. The MAC lockdown timer is set at 3,000 seconds.

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Single Device with MAC Lockdown Timeout
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Disconnecting a Device

In this example, Device A is disconnected from the port, triggering a port-down action.

The MAC entry for Device A is removed from the hardware FDB; however, the MAC entry for the device is maintained in the software. The MAC lockdown timer for this entry starts when the port goes down.

After 3,000 seconds, the MAC entry for Device A is removed from the software.

Disconnecting and Reconnecting a Device

When Device A is disconnected from the port, the resulting port-down action causes the MAC entry for Device A to be removed from the hardware FDB.

The MAC entry in software is maintained, and the MAC lockdown timer is started for the port.

After only 1,000 seconds have elapsed, Device A is reconnected to the same port and starts sending traffic. A MAC entry is created in the hardware FDB, and the MAC lockdown timer is restarted for the MAC entry in the software.

If Device A is reconnected but does not send any traffic for 3,000 seconds, no MAC entry is created in the hardware FDB, and the MAC lockdown timer will expire after reaching 3,000 seconds.

Disconnecting and Reconnecting Devices with MAC Limit Learning

In this example, a MAC learning limit of 1 has also been configured on the ports in addition to the MAC lockdown timer of 3000 seconds.

When Device A is disconnected, the resulting port-down action removes the MAC entry for Device A from the hardware FDB. The MAC entry for Device A is maintained in the software, and the MAC lockdown timer for this entry is restarted when the port goes down.

After 1000 seconds, a different device is connected to the same port and starts sending traffic. Because the MAC learning limit is set to 1 and the MAC lockdown timer is still running, the MAC address of the new device is not learned. Instead, the new MAC address is blackholed in the hardware.

When the MAC lockdown timer for Device A expires, its MAC entry is removed from the software. If the new device is still connected to the same port and sends traffic, the MAC address for the new device is learned and added to the FDB. The MAC lockdown timer for the new device is started, and the blackhole entry that was created for this device is deleted.