I have successfully upgraded both 6509's, but the mentioned â0 to 3 seconds switchover timeâ (SSO mode) in the âCatalyst 6000/6500 Series Switches with Redundant Supervisor Engines Software Image Upgrade Configuration Exampleâ was a little bit underestimated.
I experienced longer switchover due to a reset of all cards (exept the SUP720). This was a bit unexpected. Can you give any reason for this?
And will this happen again in a future upgrade?
We also wonder if the card rebooted at the same time or one per one?
Your question is answered in the document you referenced (the document id should be 71585). The explanation is under step 12 of the Software Update/Native Mode section. To summarize, after you upgrade the standby sup, it will come up in RPR mode because the IOS versions don't match.
Will it happen in a future upgrade? Yes.
Also, the linecards all reset at the time the failover occurs.