Hot Swapping CMMs
Chassis Management Module (CMM)
page 3-12
OmniSwitch 8800 Hardware Users Guide
December 2004
Hot Swapping CMMs
Hot swapping a CMM refers to the action of adding, removing, or replacing a CMM while the switch is
operating. You are not required to enter a CLI command in order to hot swap CMMs. 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, SFM, ENI, or GNI) becomes available for monitoring
functions.
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 CMMs
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.
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 a primary CMM in a redundant configuration, verify that the primary
and secondary CMMs 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interrupted due to incorrect or outdated software when the secondary CMM takes over.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 informa-
tion, refer to
