Cisco Catalyst 4500 Series Configuration Manual page 360

Supervisor Engine Redundancy Guidelines and Restrictions
If SSO mode cannot be established between the active and standby supervisor engines because of
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an incompatibility in the configuration file, a mismatched command list (MCL) is generated at the
active supervisor engine and a reload into RPR mode is forced for the standby supervisor engine.
Subsequent attempts to establish SSO, after removing the offending configuration and rebooting the
standby supervisor engine with the exact same image, might cause the
C4K_REDUNDANCY-2-IOS_VERSION_CHECK_FAIL and
ISSU-3-PEER_IMAGE_INCOMPATIBLE messages to appear because the peer image is listed as
incompatible. If the configuration problem can be corrected, you can clear the peer image from the
incompatible list with the redundancy config-sync ignore mismatched-commands EXEC
command while the peer is in a standby cold (RPR) state. This action allows the standby supervisor
engine to boot in standby hot (SSO) state when it reloads.
Here are the steps:
Step 1 Clear the offending configuration (that caused an MCL) while the standby supervisor engine is in
standby cold (RPR) state.
Step 2 Enter the redundancy config-sync ignore mismatched-commands EXEC command at the active
standby supervisor engine.
Step 3 Perform write memory.
Step 4 Reload the standby supervisor engine with the redundancy reload peer command.
• RPR and SSO requires Cisco IOS-XE Release 3.1.0SG and later releases.
SSO is not supported if the IOS-XE software is running in the LAN Base mode.
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WS-C4507R-E, WS-C4510R-E, WS-C4507R+E, and WS-C4510R+E are the only Catalyst 4500
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series switches that support Supervisor Engine 7-E and Supervisor Engine 7L-E redundancy.
SSO requires both supervisor engines in the chassis to have the same components (model and
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memory), and to use the same Cisco IOS XE software image.
• When you use WS-X45-SUP7-E and WS-X45-SUP7L-E in RPR or SSO mode, only the first two
uplinks on each supervisor engine are available. The second two uplinks are unavailable.
• The active and standby supervisor engines in the chassis must be in slots 3 and 4 for 7-slot chassis
and slot 5 and 6 for 10-slot chassis.
• Each supervisor engine in the chassis must have its own flash device and console port connections
to operate the switch on its own.
• Each supervisor engine must have a unique console connection. Do not connect a Y cable to the
console ports.
Supervisor engine redundancy does not provide supervisor engine load balancing.
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• The Cisco Express Forwarding (CEF) table is cleared on a switchover. As a result, routed traffic is
interrupted until route tables reconverge. This reconvergence time is minimal because the SSO
feature reduces the supervisor engine redundancy switchover time from 30+ seconds to subsecond,
so Layer 3 also has a faster failover time if the switch is configured for SSO.
Static IP routes are maintained across a switchover because they are configured from entries in the
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configuration file.
• Information about Layer 3 dynamic states that is maintained on the active supervisor engine is not
synchronized to the standby supervisor engine and is lost on switchover.
Software Configuration Guide—Release IOS XE 3.3.0SG and IOS 15.1(1)SG
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Chapter 10 Configuring Supervisor Engine Redundancy Using RPR and SSO on Supervisor Engine 7-E and Supervisor
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