upgrade to Gibraltar-16.12.10a checklist?

[javillan]

I have been tasked with updating our 3650 stack, wich contains 5 switches from ios 3.07.03E to Gibraltar-16.12.10a. the stacks are in install mode and will be following the cisco documentation on the upgrade process found here. I have a few questions, is there anything I should check before upgrading? This will be my first networking task after receiving my CCNA earlier this month so i want it to go smooth. Thanks for any help.

[Leo Laohoo]

What I want to know is what is the reason or business case for upgrading to 16.X.X? 

It might sound like a stupid question but it is not.  

One of the best thing about 3.6.X or 3.7.X is stability.  I have about 20 stacks of 3850 that enjoys an uptime of >3 years.

The rest of my stacks are on 16.X.X and they need to be regularly rebooted every 6 months due to instability.

[javillan]

Since im new to this, im not entirely sure. It sounds more of a higher version number/ regular updating means its better type thing coming from the higher ups. The task was worded as “lets upgrade these stacks since they havent been in years”. Can i ask what sort of instability issues you have seen with your 16.x.x stacks? 

[Leo Laohoo]

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@javillan wrote:
Can i ask what sort of instability issues you have seen with your 16.x.x stacks? 

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Do you have a whole day?  Because I can go on for days highlighting all the bugs we've hit, found, reported since the introduction of 16.3.X until 16.12.9.  

Upgrade if required but be prepared to keep an out out for memory leaks.  Since the introduction of 16.X.X, the control-plane memory leaks uncontrollably.   Memory leaks in 3.X.X. is more perverse in 16.X.X and this is why my stacks on 3.X.X have an uptime of years but stacks on 16.X.X have an uptime of months (if not weeks).  3850 (4 x switches), Firmware version: 16.12.4, Uptime: 1y43w4d

[javillan]

Cool, thanks for the input, ill have to do more research and look into this. Regarding the upgrade. Any advice? I have backups of startup and running config. Our current ios seems to be no longer available for download from cisco site. Is there anywhere/way to check if all features we are using now will seamlessly work after we upgrade. I started seeing some posts about ssh keys not working and needing to be regenerated after upgrading, but nothing official from cisco regarding this. Thanks any info helps! 

[Leo Laohoo]

Read this:  Cisco 3850: IOS-XE/Firmware Upgrade

Because the switch is on 3.7.X, the command to upgrade the firmware (Install Mode) will be different:  

software install file flash: filename.bin new force [verbose] [on-reboot]

Prepare an outage time of about 22 minutes due to mandatory micro-code upgrade.