[c-nsp] ISSU on SXF -> SXI

[Phil Mayers]

On 02/11/2010 07:48 PM, Randy McAnally wrote:
> Thanks for that information.
>
> What is the 'least problematic' method, step by step, to upgrade from SXF to
> SXI since I have dual sups?  I can handle a single reboot but don't want to
> whack any config or cause the sups to lose redundancy or need multiple or
> extended downtimes.

Load the firmware onto both sup, change the boot statement, reload the 
standby sup and it will come up in RPR mode. Force a switchover, the new 
sup will finish booting & reload the linecards.

We do this for almost all our software upgrades, and the outage it 
typically in the region of 90 seconds. There's nothing special in this 
regard about going to SXI - this is how we did it.

It's worth noting that AFAICT ISSU requires the linecards to have 
sufficient RAM to pre-load the new IOS image, and many standard 
linecards e.g. 6748-SFP/DFC-3B do not, and will therefore not do a 
"fast" ISSU. It's also relevant that for ISSU the old and new images 
have to be "compatible" and I have my doubts how often that will be the 
case...