28 BigIron RX Series Configuration Guide53-1001810-01How management module redundancy works3After the modules boot, the active module compares the standby module’s flash code andsystem-config file to its own. If differences exist, the active module synchronizes the standbymodule’s flash code and system-config file with its own.During normal operation, the active module handles tasks such as obtaining network topology andreachability information and determining the best paths to known destinations. The active modulealso monitors the standby module.The standby module functions in an active standby mode. Configuration changes made from theCLI to the active management module are also written to the standby management module even ifthey are not written to flash memory. Keeping the system-config and running-config files on bothmodules synchronized allows the standby module to assume the role of active module seamlesslyif necessary.The interface modules are not reset, as they are with the previous cold-restart redundancy feature.The interface modules continue to forward traffic while the standby management module takesover operation of the system. The new now-active management module receives updates from theinterface modules and sends verification information to the interface modules to ensure that theyare synchronized. If the new active management module becomes out-of-sync with an interfacemodule, information on the interface module can be overwritten in some cases which can cause aninterruption of traffic forwarding.Management module switchoverThe events cause the standby management module to become the active module, which is called aswitchover. Those events are as follows:• The active module becomes unavailable.• You perform a manual switchover.• You remove and replace the active management module.The following sections explain how the switchover occurs for each event.Unavailable active moduleThe following events cause an active module to become unavailable and a switchover to occur:• An active module experiences a problem significant enough to cause a reset of the module.• The active module loses power.Before a switchover occurs, the active module resets itself and sends an interrupt signal to thestandby module. The standby module then becomes the active module and the interface modulescontinue to forward traffic.The new active module begins to manage the system. When the original active module becomesavailable again or is replaced, it assumes the role of standby module.Manual switchoverIn some situations, you may want to manually switch the role of active management module fromthe currently active module to the standby module. For example, if the module in slot M2 is theactive module and the module in slot M1 is the standby module and you want the module in M1 tobe the active module and the module in M2 to be the standby module, you can perform a manualswitchover using the switchover command. For information about performing this task, refer to“Manually switching over to the standby management module” on page 34.
