Devil's Advocate - Segment Routing, Why?

Mark Tinka mark.tinka at
Sat Jun 20 10:38:13 UTC 2020

On 20/Jun/20 11:27, Baldur Norddahl wrote:

> We run the Internet in a VRF to get watertight separation between
> management and the Internet. I do also have a CGN vrf but that one has
> very few routes in it (99% being subscriber management created, eg.
> one route per customer). Why would this create a scaling issue? If you
> collapse our three routing tables into one, you would have exactly the
> same number of routes. All we did was separate the routes into
> namespaces, to establish a firewall that prevents traffic to flow
> where it shouldn't.

It may be less of an issue in 2020 with the current control planes and
how far the code has come, but in the early days of l3vpn's, the number
of VRF's you could have was directly proportional to the number of
routes you had in each one. More VRF's, less routes for each. More
routes per VRF, less VRF's in total.

I don't know if that's still an issue today, as we don't run the
Internet in a VRF. I'd defer to those with that experience, who knew
about the scaling limitations of the past.

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