Management and Configuration Guide K/KA/KB.15.15

to the standby management module. The standby management module now becomes the active
management module. Management module redundancy keeps the switch operating and reduces
network downtime.
The advantages of redundant management are:
• Maintaining switch operation if a hardware failure occurs on the active management module
• Minimizing restart time caused by the failure of a management module
• Hotswapping a failed management module with no downtime
Nonstop switching with redundant management modules
Beginning with software version K.15.01, you can use either nonstop switching or warm-standby
redundant management.
The advantages of nonstop switching are:
• Quick, seamless transition to the standby management module; no reboot is necessary
• Switching of packets continues without interruption
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.
About using redundant management
The CLI commands for redundant management are shown at the beginning of the chapter.
Additionally, some other commands are affected by redundant management (See “CLI commands
affected by redundant management” (page 492).)
Transition from no redundancy to nonstop switching
While the switch is transitioning from no redundancy mode to nonstop switching mode, no
configuration changes are allowed. The management modules are syncing information during the
transition period.
About setting the rapid switchover stale timer
After a failover has occurred, use the rapid switchover stale timer to set the amount of time that
you want route and neighbor table entries to be re-added to the FIB on the active management
module.
Layer 3 applications and protocols rely on existing routing information in the FIB. They restart and
operate as if the switch performed a quick reset.
When a failover occurs, the interface modules and the fabric modules continue forwarding Layer
3 traffic based on the information in the FIB. The transitioning standby management module marks
all routes in the FIB as "stale". The routing protocols restart, reestablish their neighbors and
reconverge. As a route is added in again, the route's stale designation is removed. After the rapid
switchover stale timer expires, the remaining stale route entries are removed. Multicast flows are
also removed; the multicast application re-adds the flows after failover completes.
480 Chassis Redundancy (8200zl Switches)