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Cisco WAN Manager User’s Guide
Version 10.5, Part Number 78-12945-01 Rev. D0, August 2003
Chapter 11 CWM to CWM Communications
Establishing Primary CWM and Secondary CWM Priority
Establishing Primary CWM and Secondary CWM Priority
In a given wide area network managed by Release 10 of CWM, the first CWM workstation to begin
operation will assume the role of Primary CWM. As other CWM workstations become active, they will
take on Secondary CWM workstation roles. The only difference in function between Primary and
Secondary CWM workstations is that the Primary CWM workstation would provide the Secondary
CWM workstations with user data when the Secondary CWM workstation launches.
Priority numbers of all Secondaries are assigned by the Primary at the time a Secondary registers with
the Primary. It is based on “first-come-first-serve” logic. All the Secondaries have the same privilege
except that the Secondary with priority 1 will take over as the Primary if the Primary shuts down.
The priority numbers of Secondaries might change in a Secondary CWMGateway process’s lifecycle.
In the following cases, the priority numbers among Secondary CWMGateways might change randomly:
• Restart the Primary CWMGateway (by watchdog)
• SwitchOver due to the Primary shutdown
• Primary ForceSwitchOver to a Secondary
This is the result of re-registration with the new Primary CWMGateway process. Priority numbers will
be re-assigned by the new Primary CWMGateway process when a Secondary registers with the new
Primary. In other words, for whatever reason the Primary CWMGateway process changes, the priority
numbers of the Secondaries will be subject to re-assignment.
It is possible that an S2 (Secondary with Priority 2) can become an S1 after the Primary CWMGateway
is restarted (by watchdog). It is also possible that an S3 can become an S1 after the switchover.
In the following cases, the priority numbers among Secondary CWMGateways will NOT change
randomly:
• Restart a Secondary (by watchdog)
• Shutdown Secondary
In these cases, if Sn (Secondary with priority n) is restarted or shutdown, any Sm (m>n) will become
S(m-1), while any Sm (m<n) will remain as Sm.
The difference between these scenarios is that in a Shutdown Secondary case, the Primary
CWMGateway process did not change.
Re-establishing Priority after CWM-CWM Communications
have been Interrupted
Primary CWM Graceful Shutdown
The first CWM to be launched assumes the role of the primary by default. Subsequently, other CWMs
launched will register with the primary CWM and each Secondary CWM is assigned a priority number
which identifies the order in which the Secondary CWM was launched with respect to the primary
CWM. Before being shutdown gracefully by the user, the CWMGateway on the primary CWM will
invoke the IDL interface (used to communicate between two CWMGateway processes), of each of the
objects corresponding to a Secondary CWMGateway. This will notify the Secondary CWM that the
primary CWM is about to go away and that it will in turn nominate the second CWM in line (priority 1)