[c-nsp] Current BGP BCP for anchoring and announcing local prefixes

[Jason Lixfeld]

On 2010-03-15, at 4:37 PM, Asbjorn Hojmark - Lists wrote:

> On Mon, 15 Mar 2010 13:08:03 -0400, you wrote:
> 
>> aggregate-address may be a reasonable solution, but I can't seem to
>> tag a community with an aggregate-address statement like I can with
>> a network statement
> 
> router bgp <asnr>
> address-family ipv4
>  aggregate-address A.A.A.A M.M.M.M attribute-map BGP-LOCAL
> 
> route-map BGP-LOCAL permit 10
> set metric 10
> set local-preference 1000
> set origin igp
> set community <whatever>

Indeed.  That not withstanding, my problem with relying on aggregate-address is that the prefix isn't announced unless it, or a candidate prefix exists in the BGP table.

When I did this all initially, my school of thought was that if there's no way to anchor these routes at the edge of the network, then an I[B]GP issue could cause a bunch of these routes to flap.  In contrast, if they are attached to a network statement and redistributed by the static null route, I[B]GP instability doesn't result in a flap of the affected prefixes.  Sure, it black holes once it hits your AS, but isn't that more desirable than a bunch of flaps?

Maybe my logic is outdated, I dunno.  If it is, I'd love to know what others are doing.