Devil's Advocate - Segment Routing, Why?

adamv0025 at adamv0025 at
Mon Jun 22 13:14:56 UTC 2020

Hi Baldur,


>From memory mx204 FIB is 10M (v4/v6) and RIB 30M for each v4 and v6.

And remember the FIB is hierarchical -so it’s the next-hops per prefix you are referring to with BGP FRR. And also going from memory of past scaling testing, if pfx1+NH1 == x, then  Pfx1+NH1+NH2 !== 2x, where x is used FIB space. 




From: NANOG < at> On Behalf Of Baldur Norddahl
Sent: Saturday, June 20, 2020 9:00 PM

I can't speak for the year 2000 as I was not doing networking at this level at that time. But when I check the specs for the base mx204 it says something like 32 VRFs, 2 million routes in FIB and 6 million routes in RIB. Clearly those numbers are the total of routes across all VRFs otherwise you arrive at silly numbers (64 million FIB if you multiply, 128k FIB if you divide by 32). My conclusion is that scale wise you are ok as long you do not try to have more than one VRF with a complete copy of the DFZ.


More worrying is that 2 million routes will soon not be enough to install all routes with a backup route, invalidating BGP FRR.


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