System information

Chapter 3 Initially Configuring the ATM Switch Router
Configuring Redundancy and Enhanced High System Availability (Catalyst 8540 MSR)
3-24
ATM Switch Router Software Configuration Guide
78-6277-03, Cisco IOS Release 12.0(13)W5(19)
Route Processor Redundant Operation (Catalyst 8540 MSR)
The ATM switch router supports fault tolerance by allowing a secondary route processor to take over if
the primary fails. This secondary, or redundant, route processor runs in standby mode. In standby mode,
the secondary route processor is partially booted with the Cisco IOS software; however, no
configuration is loaded.
At the time of a switchover, the secondary route processor takes over as primary and loads the
configuration as follows:
• If the running configuration between the primary and secondary route processors match, the new
primary uses the running configuration file
• If the running configuration between the primary and secondary route processors do not match, the
new primary uses the last saved configuration file in its nonvolatile random-access memory
(NVRAM) (not the NVRAM of the former primary)
The former primary then becomes the secondary route processor.
Note If the secondary route processor is unavailable, a major alarm is reported. Use the show
facility-alarm status command to display the redundancy alarm status.
When the ATM switch router is powered on, the two route processors go through an arbitration to
determine which is the primary route processor and which is the secondary. The following rules apply
during arbitration:
• A newly inserted route processor card always comes up as the secondary, except in cases where the
newly inserted card is the only one present.
• If the configuration is corrupted, one of the route processors comes up as primary, allowing you to
correct the situation manually.
• The primary route processor when the ATM switch is powered off continues as the primary when
the ATM switch is powered on.
• If none of the above conditions is true, the route processor in slot 4 becomes the primary.
During normal operation, the primary route processor is booted completely. The secondary CPU is
partially up, meaning it stops short of parsing the configuration. From this point, the primary and
secondary processors communicate periodically to synchronize any system configuration changes.
The following situations can cause a switchover of the primary route processor:
• The primary route processor is removed or swapped. When a route processor functioning as
primary is removed, the secondary takes over. The ATM switch router is now nonredundant until a
second route processor is inserted.
• The primary route processor is rebooted. When a route processor functioning as primary is
rebooted, the secondary takes over.
• The primary route processor fails. The secondary route processor takes over as primary, using the
last saved configuration (or the current running configuration if they have been synchronized with
the sync config command).
• A switchover is manually forced with the redundancy force-failover main-cpu command.
When a switchover occurs, permanent virtual channels (PVCs) are preserved; switched virtual channels
(SVCs) and Integrated Local Management Interface (ILMI) address states are lost, and then restored
after they are dynamically redetermined.