Extreme Networks BlackDiamond 6804 Troubleshooting Manual page 21

The MSM failover behavior depends on the following factors:
• Platform type and equippage (Summit vs. Alpine vs. BlackDiamond)
• Software configuration settings for the software exception handling options such as system
watchdog, system recovery level, and reboot loop protection. (For more information on the
configuration settings, see Chapter 4, "Software Exception Handling.")
In normal operation, the master MSM continuously resets the watchdog timer. If the watchdog timer
expires, the slave MSM will either 1) reboot the chassis and take over as the master MSM (when the
switch is equipped with MSM-64i modules), or 2) initiate a hitless failover (when the switch is
equipped with MSM-3 modules). The watchdog is a software watchdog timer that can be enabled or
disabled through CLI commands. The watchdog timer is reset as long as ExtremeWare is functioning
well enough to return to the main software exception handling loop where the critical software
exception handling tasks, such as tBGTask, handle the process of resetting the watchdog timer and
creating log entries.
• Software configuration settings for the system health check feature, or for any of the diagnostic tests
that you might choose to run manually.
For example, in the context of memory scanning and mapping, Chapter 5, "Diagnostics," contains
three tables that describe the behavior of the switch for different platform types and diagnostics
configuration:
— Table 5: Auto-recovery memory scanning and memory mapping behavior
— Table 6: Manual diagnostics memory scanning and memory mapping behavior, normal
— Table 7: Manual diagnostics memory scanning and memory mapping behavior, extended
NOTE
On switches equipped with MSM64i modules, you should periodically use the
ensure that the slave MSM and master MSM are using matched images and configurations. If not
synchronized, the slave MSM might attempt to use the image it has loaded in conjunction with the
configuration from the master MSM, a mismatch that will most likely cause the switch to behave
differently after an MSM failover, thereby defeating the intended purpose of redundant peer MSMs.
If you need to insert a new MSM, you can duplicate the contents of the NVRAM and flash memory
from an existing MSM to the newly-installed MSM using one CLI synchronization command.
NOTE
The MSM-3 uses new technology to provide "hitless" failover, meaning the MSM-3 transitions through a
failover with no traffic loss and no switch downtime, while it maintains active links and preserves layer 2
state tables. Contrast this performance to normal failover with MSM64i modules, which can take the
switch down for approximately 30 seconds. The MSM-3 makes hitless upgrades possible. It is supported
in ExtremeWare release 7.1.1 and later.
Advanced System Diagnostics and Troubleshooting Guide
The BlackDiamond Systems
command to
synchronize
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