[c-nsp] ASR9k: RIB/FIB convergence

[Thomas Schmid]

Hi,

to give you an update: TAC finally could reproduce the issue  in the lab. RIB/FIB sync is thwarted when there's a VSM module installed in the chassis (which we have in all 9k chassis). 

Let's see if they can fix it with a SMU ...

Cheers,

   Thomas


Am 02.08.2018 um 11:13 schrieb Thomas Schmid:
> Hi all,
> 
> sort of a heads up ... 
> 
> I'd be interested to hear if, and under which circumstances others are seeing this behavior,
> since the root cause is still unknown.
> 
> In the beginning there were some anecdotical complaints
> by customers that they experienced persistent reachability problems to some destinations
> when we did a scheduled maintenance in our network somewhere else. Further 
> investigations pointed to routing inconsistencies during large RIB changes. 
> 
> To give you some numbers: we found out that in our environment processing 70k BGP changes 
> takes 2-3 min to write the updates to FIB, 700k routes takes 20-30 min!!
> 
> During that period, RIB and FIB are not consistent with all the nasty consequences: 
> blackholing, routing loops etc.
> 
> Convergence time seems to be somehow related to the number of eBGP sessions on the
> box. On routers with less than 200 sessions, convergence time looks ok, from 300+
> sessions on, things get bad.
> 
> This affects both XR 5.3.3, 6.2.3 and Typhoon, Tomahawk linecards. 
> 
> TAC/BU are currently working on this, but they have a hard time to find out what's
> going wrong here. Processing the updates on the RP takes less than 1s,
> but writing the updates to the LC takes forever ...
> 
> Thanks,
> 
>    Thomas
> 
> 
> 
>