Configuring Supervisor Engine Redundancy - Cisco Catalyst 4500 Series Configuration Manual

Chapter 9 Configuring Supervisor Engine Redundancy Using RPR and SSO on Supervisor Engine 6-E and Supervisor
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Configuring Supervisor Engine Redundancy

These sections describe how to configure supervisor engine redundancy:
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OL-25340-01
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
configuration file.
Information about Layer 3 dynamic states that is maintained on the active supervisor engine is not
synchronized to the redundant supervisor engine and is lost on switchover.
Starting with Cisco IOS Release 12.2, if an unsupported condition is detected (such as when the
active supervisor engine is running Cisco IOS Release 12.2(20)EW and the redundant supervisor
engine is running Cisco IOS Release 12.1(20)EW), the redundant supervisor engine is reset multiple
times and then placed in ROMMON mode. It is important to follow the procedures outlined in the
"Performing a Software Upgrade" section on page
If you are running (or upgrading to) Cisco IOS Release 12.2(20)EWA or
Cisco IOS Release 12.2(25)EW and are using a single supervisor engine in a redundant chassis
(Catalyst 4507R or Catalyst 4510R series switch), and you intend to use routed ports, do one of the
following:
Use SVIs instead of routed ports.
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Change the redundancy mode from SSO to RPR.
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Configuration changes made to the redundant supervisor engine through SNMP synchronization and
SNMP set operations in SSO mode are not synchronized to the redundant supervisor engine. Even
though you can still perform SNMP set operations in SSO mode, you might experience unexpected
behavior.
After you configure the switch through SNMP in SSO mode, copy the running-config file to the
startup-config file on the active supervisor engine to trigger synchronization of the startup-config
file on the redundant supervisor engine. Reload the redundant supervisor engine so that the new
configuration is applied on the redundant supervisor engine.
You cannot perform configuration changes during the startup (bulk) synchronization. If you attempt
to make configuration changes during this process, the following message is generated:
Config mode locked out till standby initializes
If configuration changes occur at the same time as a supervisor engine switchover, these
configuration changes are lost.
If you remove a line card from a redundant switch and initiate an SSO switchover, and then reinsert
the line card, all interfaces are shutdown. The rest of the original line card configuration is
preserved.
This situation only occurs if a switch had reached SSO before you removed the line card.
Configuring Redundancy, page 9-8
Virtual Console for Standby Supervisor Engine, page 9-10
Synchronizing the Supervisor Engine Configurations, page 9-11
9-13.
Software Configuration Guide—Release IOS XE 3.3.0SG and IOS 15.1(1)SG
Configuring Supervisor Engine Redundancy
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