[j-nsp] Where and how to inject the default route in DFZ

[Damian Holdcroft]

Could you use a script to check CPU utilization and kill the default while
the box is crunching the feed?

If CPU @ 98% or higher, don't announce? Or similar.

On Fri, Nov 27, 2015, 19:10 Stepan Kucherenko <twh at megagroup.ru> wrote:

> I just use a generated 0/0 route which is active only if I receive
> specific prefixes from upstream(s).
>
> If you don't want 0/0 in FIB then just add no-install. Not perfect but
> better than no delay at all.
>
> I wish I could say something like "thos route is active when there are X
> routes received from this neighbor(s) and they're already in FIB" but I
> didn't find anything like that either.
>
> On 26.11.2015 18:30, Mark Smith wrote:
> > Hi list
> >
> > This is best explained by an example.
> >
> > Router R1 has a full bgp table (~550k prefixes). R1 needs to announce a
> > default route using OSPF and BGP. The worst issue is when R1 boots up.
> > Assume there is a static 0/0 route to discard. R1 brings up OSPF
> > adjacencies and starts announcing 0/0. Blackhole. Next R1 brings up BGP
> > adjacencies and starts announcing 0/0. Another blackhole. Only after R1
> has
> > received the complete route table (and pushed all prefixes to FIB) will
> the
> > blackhole disappear.
> >
> > What's the best solution to work around this? Where and how do you
> generate
> > the default?
> >
> > With OSPF or ISIS one can use overload w/ timeout. It works.
> > What about BGP? out-delay? One can use "routing-options generate route
> ..."
> > for default. But what prefix to use as contributing route? One can
> announce
> > a dummy prefix from e.g. RR, but still this does not guarantee that R1
> has
> > all necessary routes (in FIB) before announcing default. And this
> probably
> > leads to transient routing loop while R1 has default pointing to e.g.
> > loopback of RR, but routers in between see the OSPF default announced by
> R1.
> >
> > Overload timeout + generate default?
> >
> >
> > Thanks
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