Netgear XCM8810 Chassis User Manual - Page 441
Understanding the Lockdown Timer, Examples of Active and Inactive Devices
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NETGEAR 8800 User Manual new device cannot replace it until the lockdown timer for the first device has expired. This condition is true if the limit on the port is set to 1 or if the limit (greater than 1) on the port has been reached. • If a learning limit is already configured on a port when you enable the lockdown timeout feature, the configured limit will continue to apply. Existing blackholed entries are therefore not affected. If you enable this feature on a port with no configured learning limit, the default maximum learning limit (unlimited learning) is used. This section describes the following topics: • Understanding the Lockdown Timer on page 441 • Examples of Active and Inactive Devices on page 441 • Examples of Disconnecting and Reconnecting Devices on page 442 • Example of Port Movement on page 444 • Configuring MAC Address Lockdown with Timeout on page 444 • Enabling and Disabling MAC Address Lockdown with Timeout on page 444 • Displaying MAC Address Lockdown Information on page 444 Understanding the Lockdown Timer The lockdown timer works in the following ways: • When you enable this feature on a port, existing MAC entries for the port begin aging out based on the configured MAC lockdown timer value. • If you move a device from one port to another, its MAC address entry is updated with the new port information, including the lockdown timer value configured for that port. • If this feature is enabled on a port and you decrease the lockdown timer value for that port, all of the MAC FDB entries for that port will time out and be removed at the next polling interval. • When you disable the lockdown timer on a port, existing MAC address entries for the port will time out based on the FDB aging period. Examples of Active and Inactive Devices Figure 28 shows three devices (A, B, and C) connected through a hub to an NETGEAR device with MAC lockdown timeout configured on the ports. When each device starts sending traffic, the source MAC address of the device is learned and FDB entries are created. The MAC lockdown timer is set at 100 seconds. Chapter 17. Security | 441
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