software upgrade on supervisor engine redundancy

[nitass]

Hello there,

Does anyone please advice me why software upgrade on supervisor engine redundancy has to operate in RPR mode? Can we do in SSO mode?

I have seen it on Catalyst 4500 Series Switch Cisco IOS Software Configuration Guide but did not see any explanations.

?Reloads the redundant supervisor engine and brings it back online (using the new release of the Cisco IOS software).

Note Before proceeding to Step 10, ensure that the switch is operating in RPR mode.?

http://www.cisco.com/en/US/products/hw/switches/ps4324/products_configuration_guide_chapter09186a008062ce91.html

Please advice.

Thanks in advance,

Nitass

[Edison Ortiz]

Because when you are running in RPR mode, it allows you to run a different IOS version in the primary/active SUP engine while performing the upgrade in the secondary engine. When running SSO, both engines must run the same IOS version at all times, therefore you must reboot both at the same time in order to regain the config-sync.

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Thanks

[nitass]

Thanks for reply. Did you mean we have to change to RPR mode before upgrading software? Then change back to SSO mode.

Am I correct?

Thanks in advance,

Nitass