We would like to upgrade IOS software image on our Cisco WS-C6509.
We've got redundant Supervisor Engine 720/MSFC3:
5 2 Supervisor Engine 720 (Active) WS-SUP720-3B SAL11477LF5
6 2 Supervisor Engine 720 (Hot) WS-SUP720-3B SAL11477L4J
The device is operating so we'are creating low impact towards the environment.
We're thinking of using SSO mode but we read that when I reset the standby Supervisor Engine the version mismatch message brings about a reload all modules (Redundancy Mode changes from SSO to RPR).
Is It correct?
Is there another method to upgrade without loosing any data?
I think you need to reload the chassis because the mismatch between the running one and the standby don't allow to run on redundancy.
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You can reset or force a redundancy switch over for one supervisor. This is "hitless" but supervisors will no longer be in redundancy. It usually takes several minutes for inactive supervisor to reload.
When you reset or redundancy switch over the 2nd supervisor, the chassis will go off-line for several minutes. (Note: switching over to the 2nd supervisor already running different IOS seems to be just a little quicker, but line cards are restarted which is what causes the "hit".)
depending on the initial SW image and the new SW image the chassis might support in service software upgrade.
read the following chapter from 12.2SX C6500 configuration guide
However, also ISSU is not hitless so you need a maintenance time window.
Hope to help