Dell PowerConnect B-RX BigIron RX Series Configuration Guide v02.7.02 - Page 100

3 How management module redundancy works After the modules boot, the active module compares the standby module's flash code and system-config file to its own. If differences exist, the active module synchronizes the standby module's flash code and system-config file with its own. During normal operation, the active module handles tasks such as obtaining network topology and reachability information and determining the best paths to known destinations. The active module also monitors the standby module. The standby module functions in an active standby mode. Configuration changes made from the CLI to the active management module are also written to the standby management module even if they are not written to flash memory. Keeping the system-config and running-config files on both modules synchronized allows the standby module to assume the role of active module seamlessly if 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 takes over operation of the system. The new now-active management module receives updates from the interface modules and sends verification information to the interface modules to ensure that they are synchronized. If the new active management module becomes out-of-sync with an interface module, information on the interface module can be overwritten in some cases which can cause an interruption of traffic forwarding. Management module switchover The events cause the standby management module to become the active module, which is called a switchover. 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 module The 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 the standby module. The standby module then becomes the active module and the interface modules continue to forward traffic. The new active module begins to manage the system. When the original active module becomes available again or is replaced, it assumes the role of standby module. Manual switchover In some situations, you may want to manually switch the role of active management module from the currently active module to the standby module. For example, if the module in slot M2 is the active module and the module in slot M1 is the standby module and you want the module in M1 to be the active module and the module in M2 to be the standby module, you can perform a manual switchover using the switchover command. For information about performing this task, refer to "Manually switching over to the standby management module" on page 34. 28 BigIron RX Series Configuration Guide 53-1001810-01