Hotswapping management modules

There are a number of events that can cause the active management module to switchover to the standby management module when management module redundancy is enabled:

In all of these cases, the standby management module takes control and performs the actual switchover. The reason for the switchover is entered in log messages on the newly active management module and to any configured Syslog servers.

When a switchover occurs, the features that support nonstop switching continue to operate in an uninterrupted manner. See Nonstop switching features for a list of the supported features.

The features that do not support nonstop switching perform as if the switch had just finished booting; however, no actual boot time occurs.

	NOTE: When meshing configuration changes are made on a redundant management system, you must execute write mem and then the boot system command to boot both management modules for the changes to be activated. Meshing is not supported by nonstop switching.

	NOTE: If the switch is a querier and a failover occurs, the querier continues to be the same on the standby management module; no new querier election process occurs on the standby management module.

There are some events for which a switchover is not triggered:

If the uncommon situation occurs where the active management module (MM1) is trying to reboot and the standby management module (MM2) also crashes, the switch attempts to recover from the crash and eventually the standby management module becomes the active management module if it passes self-test. However, traffic can be disrupted for as long as five minutes before the newly active management module (MM2) has finished rebooting.

You can hotswap out the active management module and have switch operations taken over by the standby management module by following the correct shutdown procedure on the active module using the MM Shutdown button. When the MM Shutdown button is pressed, any file synchronization in progress completes before the shutdown begins, and then a graceful shutdown of that management module occurs.

If you have disabled management module redundancy with the no redundancy management-module command, or the standby module failed selftest, the Dwn LED does not turn green to indicate it is OK to hotswap out the active management module.

	NOTE: If you remove the active management module without pressing the MM Shutdown button, any files that may have been in the process of synchronizing will not finish synchronizing to the standby module and all file transfer is aborted.

If another management module is hotswapped in while there is an active management module booted up, the newly hotswapped management module becomes the standby module.

No negotiating is needed as to which module becomes the active management module, because there is already a functioning active management module. However, the following conditions must be met to determine if the hotswapped module can become a standby management module:

In nonstop switching mode—The active management module's files and features are synced with the standby management module. Heartbeats are sent back and forth, and the standby management module is ready to quickly take over in the event of a switchover or a failure on the active management module.

In warm-standby mode—The standby management module partially boots up and heartbeats are sent back and forth with the active management module.