Chassis Initialization; Chassis Operation; Chassis Communication; Chassis Switchover - Cisco ASR 5000 Administration Manual

Chassis Initialization

Chassis Initialization
When the chassis are simultaneously initialized, they send Hello messages to their configured peer. The peer
sends a response, establishes communication between the chassis, and messages are sent that contain
configuration information.
During initialization, if both chassis are misconfigured in the same mode - both active (primary) or both
standby (backup), the chassis with the highest priority (lowest number set with the ICSR priority command)
becomes active and the other chassis becomes the standby.
If the chassis priorities are the same, the system compares the two MAC addresses and the chassis with the
higher SPIO MAC address becomes active. For example, if the chassis have MAC addresses of
00-02-43-03-1C-2B and 00-02-43-03-01-3B, the last 3 sets of octets (the first 3 sets are the vendor code) are
compared. In this example, the 03-1C-2B and 03-01-3B are compared from left to right. The first pair of octets
in both MAC addresses are the same, so the next pairs are compared. Since the 01 is lower than the 1C, the
chassis with the SPIO MAC address of 00-02-43-03-1C-2B becomes active and the other chassis the standby.

Chassis Operation

This section describes how the chassis communicate, maintain subscriber sessions, and perform chassis
switchover.

Chassis Communication

If one chassis in the active state and one in the standby state, they both send Hello messages at each hello
interval. Subscriber sessions that exceed the checkpoint session duration are included in checkpoint messages
that are sent to the standby chassis. The checkpoint message contains subscriber session information so if the
active chassis goes out of service, the backup chassis becomes active and is able to continue processing the
subscriber sessions. Additional checkpoint messages occur at various intervals whenever subscriber session
information is updated on the standby chassis.
The SRP Configuration mode checkpoint session command includes a number of keywords that allows you
to:
• Set the type of compression algorithm to be used for SRP payload messages.
• Set the amount of time the chassis waits before check pointing an existing call session. Checkpoints can
• Enable the NACK feature for handling checkpointing messaging on the Standby chassis.
• Configure the interval between the sending of macro-checkpoints (full checkpoints) between the active
For additional information see the Service Redundancy Protocol Configuration Mode Commands chapter in
the Command Line Interface Reference.

Chassis Switchover

If the active chassis goes out of service, the standby chassis continues to send Hello messages. If the standby
chassis does not receive a response to the Hello messages within the dead interval, the standby chassis initiates
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be separately set for IMS and/or non-IMS sessions.
and standby chassis.
Interchassis Session Recovery