Greetings!
For a 5400R switch with dual management modules, only one module is active at a time, with the second module acting as a standby that will take over in the event of a failure of the active module.
If you connect both modules to your management network, the link on the standby will automatically be enabled and will assume the configured switch OoBM IP address (configured from the 'oobm' context in the CLI) after a failover event.