[c-nsp] suppress bgp updates?

[Gert Doering]

Hi,

On Tue, Nov 23, 2010 at 07:45:47AM -0500, Randy McAnally wrote:
> What if the customer wants to stop announcing through you?  Isn't your config
> basically a permanent announcement?

If we do BGP with a customer, we don't nail down the announcement at
our side (because if we did, we'll blackhole the customer if their link
to us goes down but their "other uplink" - which usually is the reason
to have BGP-to-ISP - is still available).

Not that I haven't seen ISPs do this, but that should be punishable 
by law...

So there's two cases here:

 - customer has PI, wants *us* to announce it, no other ISP involved
   -> we announce their /24 (e.g.), have a static null-route for that,
   and all interiour routing happens on the two /25s.

   customer network is at all times seen originated by our AS.

 - customer has his own netblock, his own AS number, and two different
   uplink ISPs ("classical BGP multihoming") - we accept and transit
   the customer announcement.

   customer network is at all times seen originated by his own AS, and
   the AS path might contain our AS or might not (however the topology
   looks like at this point).  The network is NEVER originated by our AS.

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de