[j-nsp] EX4200 virtual chassis problem, master going into linecard mode

[Pavel Lunin]

--> so then in a 2node VC one node is Master one node is backup
> If they split the master will go down but the backup should survive as it
> is
> still half of the original cluster
>
> So this means you should make the part you want to survive to be the
> backup-RE and not the master-RE
>
> --- or did I miss something ?!
>
>

My philosophy is that a default use case of a two nodes VC (and nearly only
use case of a VC at all) should be some LAG-based redundancy, when two
switches are racked next to each other, connected with two twinax cables
and should never split. Of course, technically they can, but a lot of other
bloody things, which are out of our control, can happen to them: software
bug, misconfiguration, uncontrolled hardware failure like bite errors cased
by an overheated SFP, drunk worker with an angle grinder etc.

All the exotic cases like geographically distributed VCs etc are, in my
opinion, an exercise for the folks who can't figure out what routing
protocols are made for. So this should not be the default use case, and the
default software behavior should not be adapted to such scenarios.

Thus in a two-nodes VC, a *real* failure scenario is a switch failure. When
split-detection is enabled, two-nodes VC will only survive in 50% of switch
failure cases (if backup RE dies, VC dies, if master RE dies, VC survives).
So in fact it's just no better than a signle non-redundant switch. It's
worse, in fact, as the added complexity and false expectations are, in
fact, more expensive currency than a controlled service outage.

Cheers,
Pavel