[j-nsp] Many contributing routes

[Thomas Bellman]

On 2017-08-09 09:05, Vincent Bernat wrote:

> I am generating a default route to distribute with a policy statement
> like that:
> 
> #v+
>     policy-statement v4-DEFAULT-ROUTE-GENERATE {
[...]
>     }
> #v-
> 
> This works just fine but there are a lot of contributing routes (about
> 400k) to the generated route. Is it harmless or will I run into trouble
> for that?

That is a pretty common thing to do when you inject a default
route into your IGP (OSPF or ISIS) from your BGP-talking border
routers.  At least for those of us who are end-users, and not
ISPs ourselves, since our internal routers often do not handle
a full Internet table.  If you have a full Internet BGP feed
in your border router, you will of course then get hundreds of
thousands of contributing routes.  If this was problematic,
lots of people would complain...

Usually, you would use an 'aggregate' route for that (i.e. 'edit
routing-options aggregate'), or a 'generate' route ('edit routing-
options generate') with an explicit discard or reject target, not
retaining the nexthop from any of the contributing routes.  My
understanding is that if you use a generate route that keeps the
nexthop from some contributing route, you usually have fairly few
contributors, but I would not expect it to be a problem having
400k contributing routes.


	/Bellman

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