Redundant Supervisors - Cisco Catalyst 2000 Configuration Handbook

42 Cisco LAN Switching Configuration Handbook

3-6: Redundant Supervisors

When identical Supervisor hardware is placed in slots 5 and 5 of a Catalyst 6500 se-
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ries switches, one Supervisor is active, and the other is in standby mode.
If a failure occurs, the redundant Supervisor takes over switch functionality.
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Configuration files and operating system files are synchronized between switches.
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■ Layer 2 tables are synchronized between the supervisors for quick transitions
between modules.
Parameters such as the Layer 2 synchronization and operating system synchroniza-
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tion can be managed for the modules.
■ Catalyst 6500 series switches provide both Layer 2 and Layer 3 synchronization
within the same operating system and configuration.
By placing identical Supervisor hardware and software in slots 5 and 5 of a Catalyst 6500
series switch, you have activated system redundancy. No parameters enable you to acti-
vate this feature. The first Supervisor to come online is active, and the second one is in
standby mode. The standby Supervisor has an orange system light, and the console port
is not active. However, the interfaces on the module are active.
You can remove or insert Supervisor cards while the switch is powered on. If a second
Supervisor is added or a standby Supervisor is replaced, the card inserted into the switch
goes through the power-on diagnostics but does not test the backplane (because this
would interrupt traffic flow) and then goes into standby mode. The standby Supervisor
becomes active if there is a failure in the primary Supervisor or if you force a change by
resetting the primary Supervisor.
The Supervisor and MSFC are each responsible for different functions and protocols
(Layer 2 versus Layer 3). However, the system is dependent on both engines being avail-
able for proper operation. Failure of either the Supervisor or the MSFC in
RPR/RPR+/SSO mode causes a switchover from the active Supervisor to the standby
Supervisor/MSFC.
RPR: The first redundancy mode of operation introduced in Cisco IOS Software. In
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RPR mode, the startup configuration and boot registers are synchronized between
the active and standby supervisors; the standby is not fully initialized; and images be-
tween the active and standby supervisors do not need to be the same. Upon
switchover, the standby Supervisor becomes active automatically, but it must com-
plete the boot process. In addition, all line cards are reloaded, and the hardware is re-
programmed. The RPR switchover time is two or more minutes.
■ RPR+: An enhancement to RPR in which the standby Supervisor is completely boot-
ed and line cards do not reload upon switchover. The running configuration is syn-
chronized between the active and the standby supervisors. All synchronization activ-
ities inherited from RPR are also performed. The synchronization is done before the