Cisco Cisco Packet Data Gateway (PDG)
Interchassis Session Recovery
▀ Overview
▄ VPC-VSM System Administration Guide, StarOS Release 19
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Overview
Instance-to-Instance Communication
VPC-VSM instances configured to support ICSR communicate using periodic Hello messages. These messages are sent
by each instance to notify the peer of its current state. The Hello message contains information about the instance such
as its configuration and priority. A dead interval is used to set a time limit for a Hello message to be received from the
instance’s peer. If the standby instance does not receive a Hello message from the active instance within the dead
interval, the standby instance transitions to the active state.
by each instance to notify the peer of its current state. The Hello message contains information about the instance such
as its configuration and priority. A dead interval is used to set a time limit for a Hello message to be received from the
instance’s peer. If the standby instance does not receive a Hello message from the active instance within the dead
interval, the standby instance transitions to the active state.
In situations where the SRP link goes out of service, a priority scheme is used to determine which instance processes the
session. The following priority scheme is used:
session. The following priority scheme is used:
route modifier
chassis (VPC-VSM instance) priority
VPC-VSM MAC address
Checkpoint Messages
Checkpoint messages are sent from the active instance to the standby instance. These messages are sent at specific
intervals and contain all the information needed to recreate the sessions on the standby instance, if that instance were to
become active. Once a session exceeds the checkpoint duration, checkpoint data is collected on the session. There are
full checkpoint messages and micro-checkpoint messages.
intervals and contain all the information needed to recreate the sessions on the standby instance, if that instance were to
become active. Once a session exceeds the checkpoint duration, checkpoint data is collected on the session. There are
full checkpoint messages and micro-checkpoint messages.
AAA Monitor
AAA servers are monitored using the authentication probe mechanism. AAA servers are considered Up if the
authentication-probe receives a valid response. AAA servers are considered Down when the max-retries count
specified in the configuration of the AAA server has been reached. SRP initiates a switchover when none of the
configured AAA servers responds to an authentication probe. AAA probing is only performed on the active VSM.
authentication-probe receives a valid response. AAA servers are considered Down when the max-retries count
specified in the configuration of the AAA server has been reached. SRP initiates a switchover when none of the
configured AAA servers responds to an authentication probe. AAA probing is only performed on the active VSM.
Important:
A switchover event caused by an AAA monitoring failure is non-revertible.
If the newly active instance fails to monitor the configured AAA servers, it remains as the active instance until one of
the following occurs:
the following occurs:
a manual switchover
another non-AAA failure event causes StarOS to switchover
a CLI command is used to clear the AAA failure flag and allow the instance to switch to standby
Maximum Number of sessmgrs
The maximum number of session manager tasks (sessmgrs) supported by a VPC-VSM instance is 32. For ICSR you
must run the following command on both the Active and Standby instances:
must run the following command on both the Active and Standby instances: