[c-nsp] ASR9k: RIB/FIB convergence

[adamv0025 at netconsultings.com]

> Thomas Schmid
> Sent: Monday, August 27, 2018 3:01 PM
> To: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] ASR9k: RIB/FIB convergence
> 
> Hi,
> 
> Am 21.08.2018 um 16:35 schrieb 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 ...
> >
> 
> latest news: FIB updates are sent via the punt-switch (sort of regular
> ethernet switch on the RP) as multicast to all LCs. On A99-RP2-SE RPs this
> switch has flow control enabled. Now, the VSM LC answers to these updates
> with PAUSE frames and therefore the switch throttles the update rate to all
> LCs close to zero.
> 
> Good news: as a workaround you can disable flow-control to the punt-switch
> via CLI for specific LCs.
> 
> I'm reluctant to share the CLI command here because it's very hardware
> specific and I don't want anybody to run into problems just because their
> hardware is slightly different from ours.
> 
> Cisco will provide a SMU in the next weeks that either disables flow-control
> on these LC or changes the throttle thresholds (not decided yet).
> 
Thank you very much for the update,

This begs a question if the flow-control is enabled (i.e. the punt sw reacts to pause frames), under what circumstance can this happen with other line-cards.
In other words under which circumstances do various line-cards issue pause frames, or is just VSM capable of sending pause frames (an artefact of being a sort of "PC") 


adam

netconsultings.com
::carrier-class solutions for the telecommunications industry::