On Wed, 1 Sept 2021 at 20:35, Chuck Anderson via juniper-nsp <juniper-nsp@puck.nether.net> wrote:
> Eventually during the ISSU process, the line card software needs to be > upgraded. During that part, each line card goes offline one at a > time. If you have multiple line cards, design your network such that > redundant network paths are connected across different cards to > prevent a total outage when each line card is upgraded one-by-one. Disclaimer: I do not use ISSU nor do I plan to use it, it is complex and I've been hurt before with non-obvious failure modes after the box is left in an unknown state, this is vendor agnostic fear I have and I am currently not seeking help to overcome it. https://www.juniper.net/documentation/us/en/software/junos/high-availability/topics/topic-map/unified-issu-enhanced-mode.html Enhanced mode is an in-service software upgrade (ISSU) option available on MPC8E, MPC9E, and MPC11E line cards that eliminates packet loss during the unified ISSU process The changes in hardware that affect MPC behaviour are mostly the microcode that the lookup engines run, in trio these are collections of identical cores called PPE (packet processing engine). In theory we could put one PPE at a time out of service, and restart it with new ucode, until we're all done, having N-1/N of nominal PPS capacity during upgrade (I think EA has 96 PPE, so 98.95% during upgrade), And in fact this is what 'hyper mode' does, Trio has ucode compatible history of over a decade, without running hyper mode the PPEs are running the old +decade old collection of code, with hyper mode the PPEs are running new rewrite of the ucode. Newer hardware is hyper mode only, older hardware it is operator choice which generation of ucode to run. -- ++ytti _______________________________________________ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp