Devil's Advocate - Segment Routing, Why?

Mark Tinka mark.tinka at
Sun Jun 21 07:56:05 UTC 2020

On 20/Jun/20 22:00, Baldur Norddahl wrote:

> 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.

I recall a number of networks holding multiple VRF's, including at least
2x Internet VRF's, for numerous use-cases. I don't know if they still do
that today, but one can get creative real quick :-).

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

I have a niggling feeling this will be solved before we get there.

Now, whether we can afford it is a whole other matter.

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