[c-nsp] route processor redundancy basics (RPR)

Lukas Tribus luky-37 at hotmail.com
Tue Aug 2 03:44:38 EDT 2016


> RPR: standby RP is partially initialised. That is, only the startup-config
> of the active router and standby router are sync'ed.

Correct.


> I lost about 1 or 2 minutes of pings during this stage, then RP1 stabilised
> and the pings started going through.
> 
> Is this expected behaviour?

Yes. You just said it yourself: RPR only sync's the startup configuration, meaning that a "switchover" (which actually isn't a switchover) will reload both RP's.


> Also, why would anyone use RPR over SSO?

RPR: RP redundancy (not a switchover)
SSO: stateful switchover


You can use RPR (which again, is not a switchover) if you have a problem with SSO. For example if you have reason to believe that an inconsistency (due to a bug) may spread to the secondary RP due to stateful synchronization, and you don't need an actual switchover (but only hw redundancy).

We have some ancient GSR12k as P (therefor no customers are connected to those boxes) with dual RP configured in RPR, because we don't care about stateful switchover, as there are backup paths around the box. We do want the box to come back after a few minutes if there is a hardware failure though.


On a box with single homed customers connected to it I would always run SSO.



Regards,

Lukas


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