[c-nsp] Change BGP default-originate to IGP?

[Blake Dunlap]

Another option is to lock the static default route to a tracked object, and
based that object on eem scripting or something similar which has a built
in delay after the bgp peer reaches X prefix count.

It's definitely more creaky though. Something you should keep in mind is
you're going to have some blackholing regardless of what you do, due to the
return path experiencing the same issue as it propagates out. It's just a
question of what levels you are comfortable with.

-Blake

On Thu, Sep 27, 2012 at 3:40 AM, Adam Vitkovsky <adam.vitkovsky at swan.sk>wrote:

> So if I understood it correctly you are concerned that the router will
> start
> to originate the default prior to receiving full BGP table from its
> upstream
> right?
> The simplest solution would be to place a static default route pointing to
> the upstream -so in case of the above happens the router wouldn't blackhole
> till it gets the full feed.
> Or you can base the condition of default advertisement on several prefixes
> from all around the place instead of just one -but trying to match e.g. 10
> prefixes from 400k well...
> The problem with this though is that on IOS you can't AND the "match ip
> address" statements under the route-map only OR -applies to all the match
> statements of the same kind.
> So you could use static routes for the list of desired prefixes each with a
> high AD -redistribute them into bgp with specific community and match for
> the prefixes+community in "non-exist map".
> So once you'll get all the prefixes from BGP -only after all cease to exist
> in the bgp table with the specific community of yours -the router will
> start
> to advertise the default route.
>
> adam
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Tom Lanyon
> Sent: Thursday, September 27, 2012 4:58 AM
> To: David Prall; cisco-nsp
> Subject: Re: [c-nsp] Change BGP default-originate to IGP?
>
> Is there a specific order in which BGP updates are
> sent/exchanged/processed?
>
> The concern I have with tracking upstream routes is that the route tracked
> would need to be one of the last routes received (if not the last) to
> ensure
> that the router has full visibility.  This seems quite non-deterministic
> and
> so potentially fraught with 'weirdness'.
>
> Thanks,
> Tom
>
> On 27/09/2012, at 12:19 PM, David Prall wrote:
> > Why not use selective advertisement of the default based on receiving
> > a specific route from your carrier or an upstream you know to be stable.
> >
> > http://www.cisco.com/en/US/docs/ios/12_3/iproute/command/reference/ip2
> > _n1g.h
> > tml#wp1037042
> >
> > David
>
>
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