Installation guide

Functional Description
6
Cisco IOS 11.2(15)GS2
The failover event is logged, and can be viewed via the show redundancy arbitration EXEC
command.
Field Diagnostics
You can run field diagnostics on the secondary GRP, from the primary GRP, while the router is
handling traffic. Make certain before you start the diagnostics that the console you are using is not
connected via the secondary GRP. When the diagnostics finish running, the secondary GRP remains
at the ROM monitor prompt and must be manually rebooted.
Note Field diagnostics are usually run under the guidance of qualified support personnel.
System Logs
The primary GRP broadcasts system log messages to the secondary, where they are saved. When a
failover occurs, you can see the system log messages that preceded this event by issuing the
show log slot number EXEC command on the new primary, where the slot number is that of the
failed primary.
Issuing the show log slot number command, where the slot number is that of a linecard rather than
the slot number of the failed GRP, shows messages sent to the previous primary, followed by a
failover message and the messages that were sent to the new primary.
Crash Dumps
Using the exception dump global configuration command, the GRP can be configured to create a
core file (also called a crash dump) when it fails. When the primary GRP fails, it waits for the
secondary GRP to become the new primary. Once the new primary GRP is running, it checks its
configuration. If exception dump is enabled, it receives the core files from the failed GRP. The
primary writes the core files to the network the same as it would for any failed line card.
A timer runs on the failed GRP. If the secondary GRP does not take over as the new primary, the
failed primary GRP will reboot and resume operation as the primary. If the failed GRP reboots, it
loses the core file.
Additional Diagnostic Aids
The show redundancy EXEC command shows the current redundancy status. Various options to
this command can display additional details of the arbitration mechanism, traces of the arbitration
protocol, or details of the secondary GRP.
The show boot EXEC command shows details of both primary and secondary GRP boot parameters.
The show user EXEC command is useful to discover which console port you are using— the
console port on the primary GRP, the console port on the secondary GRP, or some other connection.
Additional GRPs
The redundant support mechanism is designed for two GRPs in a single chassis. If three or more
GRPs are installed in a router chassis, the arbitration mechanism identifies a primary and secondary
GRP and temporarily disables any additional GRPs from participating in the arbitration process.