[j-nsp] ISSU offlined mpc - why?

[Mark Tinka]

On 9/1/21 18:44, Mike via juniper-nsp wrote:

> Hello,
>
>     I did an issu upgrade on an MX240 with dual routing engines, going 
> from 15.1R6 to 17.4R2, and I had reviewed the fine manuals 
> particularly concerning advance steps to ensure nonstop routing and so 
> forth. But during the upgrade (near the very end), the router did 
> offline my MPC 3D 16x 10GE, resulting in loss of routing for 5 
> minutes. According to juniper in their docs that state that:
>
> "Unified ISSU is supported with Junos OS Release 17.4R1 for MX Series 
> routers with MPC-3D-16XGE-SFPP"
>
>     my expectations were that the card would stay online and there 
> would be little to no operational impact, but this clearly wasn't the 
> case. I am just wondering if anyone can tell me why this might have 
> been the case and in the future what steps I would need to take to 
> ensure this both otherwise stays on the air during a future software 
> update?

I haven't thought about ISSU since 1 year after it first made an 
appearance across vendor platforms.

Are people still actually considering it, or even trying to use it?

It didn't seem - to me anyway - that it had any chance of delivering on 
its promise more than a decade ago. I can't fathom that this situation 
has changed in 2021, but I could be wrong.

Mark.