[j-nsp] ISSU offlined mpc - why?

[Jonas Frey]

> 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"

I think that might be a misunderstanding. Shouldnt it read "is supported starting with Junos Release 17.4R1"?

(That would make sense since some of the cards listed on that paragraph, e.g. MPC7EQ-MRATE-RB, were only supported since JunOS 16+)

Because then it would be clear - since you are coming from 15.1R6 this release wouldnt support it and jumping to 17.4R2 would
cause the MPC reboot.

-Jonas