[c-nsp] (no subject)

[Vincent C Jones]

The way I've dealt with this in the past (a trick I learned from Barry)
is to ask for full routes (and no default), filter out ALL prefixes
except for those of associated with a few far away root name servers,
and then generate a default conditional on reachability of at least one
name server. It gets a little ugly, because you need to ensure you only
generate the default if the route to the name servers is through your
upstream, which means that all BGP routers in your AS must not pass on
those prefixes plus you have to keep track on an ongoing basis of
changes in the prefixes containing the root name servers or their IP
address. 

Disclaimer: Have not tested this approach with IPv6 because I retired
before I had any clients who cared :-] but I've used it with IPv4 since
the days of 2501 routers.

Vince 



On Thu, 2014-10-02 at 11:46 -0700, Paul Wozney wrote:
> Okay so I've got two BGP routers here, accepting partial routes - one
> carrier to each router. Each carrier advertises a default route. I use an
> as-path filter to limit learned routes to those of the carrier +1 ASn:
> 
> ip as-path access-list 11 permit ^NNNN_[0-9]*$
> 
> 
> One carrier has now had two outages in the last year where they've lost
> their upstream. They continue to advertise a default route to us, so our
> network experiences failures until we kill the link.
> 
> It strikes me that if we had FULL routes (and no default route accepted) we
> could react automatically to failures like this - we could share tables
> between the routers and if one carrier lost half their routes we'd pick
> them up from the other router.
> 
> Is this just how life with partial routes is? Or is there something else I
> can do?
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