How the management modules interact
When the switch boots up, the management modules run selftest to decide which is the active module and which is the standby module. The module that becomes active finishes booting and then brings up the interface modules and ports.
If you are using nonstop switching mode, the standby management module is synced continuously with the active management module so that all features and config files are the same on both management modules. The standby management module is ready to become the active management module. If the active management module fails or if there is a manual switchover, switching continues without interruption.
If you are using warm-standby mode, the standby module boots to a certain point, syncs basic files such as the config and security files, and finishes booting only if the active management module fails or you choose to change which module is the active module.
The two management modules communicate by sending heartbeats back and forth.