Chassis Management Module (CMM)
Hot Swapping CMM Modules
OmniSwitch 7700/7800 Hardware Users Guide
April 2005
page 4-11
Hot Swapping CMM Modules
Hot swapping a CMM refers to the action of adding, removing, or replacing a CMM module while the
switch is operating. You are not required to enter a CLI command in order to hot swap CMM modules.
This function can be performed on the fly by simply removing the module from the switch chassis.
Module Presence Signalling
On-the-fly module removal is provided through the presence signalling function. All modules in the
switch send out “presence signals.” When a module sends out this signal, it is essentially advertising to all
other modules in the switch that it is present in the chassis. When a module is present, information such as
its module type (primary CMM, secondary CMM, ENI, or GNI) becomes available for monitoring func-
tions.
The presence signal is controlled through a shortened connector pin that interfaces with the switch’s back-
plane. Because this connector pin is shorter than the module’s other backplane connectors, the presence
signal connection is the first to become interrupted when a board is removed from the chassis. This allows
the switch additional time (approximately 5 ms) to complete the current transfer of data before the module
is completely disconnected. (In order to avoid data loss, the switch immediately stops incoming traffic and
flushes outgoing traffic on the module being removed.)
Note.
Although presence signalling is designed to maintain data flow on the switch during the hot swap
procedure, uninterrupted data flow cannot be guaranteed. As a result, you should not hot swap CMM
modules during critical network activity.
Hot Swap Requirements
Important.
There are important conditions that must be met before a CMM can be hot swapped. Be sure
to read the information below before attempting to hot swap a CMM module.
Removing or Replacing CMMs
You must have CMM redundancy before removing or replacing a CMM. If the switch has only one CMM
installed and you attempt to hot swap the module, all switch management functions as well as network
data flow will be terminated. For important information on CMM redundancy, refer to
Also, before removing or replacing the primary CMM in a redundant configuration, verify that the
primary and secondary CMM modules are synchronized. Otherwise, data flow and switch management
functions may be interrupted due to incorrect or outdated software when the secondary CMM takes over.
For more information, refer to
“Synchronizing the Primary and Secondary CMMs” on page 4-10
.
