Partial vs Full tables

Fri Jun 5 08:07:32 UTC 2020

On Fri, 5 Jun 2020 at 10:48, Tore Anderson <tore at fud.no> wrote:

> We started taking defaults from our transits and filtering most of the
> DFZ over three years ago. No regrets, it's one of the best decisions we
> ever made. Vastly reduced both convergence time and CapEx.

Is this verbatim? I don't think there is a use case to ever carry
default route in dynamic routing.

In eBGP it should be some reliable indicator of operator network being
up, like their own aggregate route, they have incentive to originate
this correctly, as it affects their own services and products. So
recurse static default to this route. Otherwise you cannot know how
the operator originates default, they may just blindly generate it in
the edge, and if edge becomes disconnected from core, you'll
blackhole, compared to static route solution where the aggregate would
not be generated by edge routers by any sane operator due to
self-preservation instinct, you'd be able to converge instead of
blackhole.

In internal network, instead of having a default route in iBGP or IGP,
you should have the same loopback address in every full DFZ router and
advertise that loopback in IGP. Then non fullDFZ routers should static
route default to that loopback, always reaching IGP closest full DFZ
router.

-- 
  ++ytti