[c-nsp] BGP - Announcing routes to Internet providers.

[Scott Granados]

Drew, network statements are for the weak.:)
(I'm kidding of course) but there is a better way.
You should use community tagging in combination with prefix lists and route 
maps.  The idea is that you announce routes according to a tag and the 
behavior of the announcements depends on the specific tag applied.  For 
example, you could tag routes as peers, transits, global announce, etc and 
formulate the type of feeds you give your customers by filtering against 
communities so a customer wants peers and customers only you could match the 
two appropriate community tags.  This also allows you to tag the communities 
you globally announce uniquely and make the announcements in a unified way 
at your edges.  If you accompany this method with the appropriate 
redistribute static, redistribute connected, etc and use route maps to 
control this behavior you can remove the need for network statements 
completely and greatly decrease the things you need to modify and as a 
result the possible mistakes.  The other upside here is you can mark your 
more specifics as do not export and better control traffic internally better 
directing the traffic in your example.  It also allows you to accept 
communities from your customers and have automatic actions taken based on 
the tags they apply.  Let me know if you need some configuration examples.



----- Original Message ----- 
From: "Drew Weaver" <drew.weaver at thenap.com>
To: "Cisco-nsp" <cisco-nsp at puck.nether.net>
Sent: Monday, January 04, 2010 12:35 PM
Subject: [c-nsp] BGP - Announcing routes to Internet providers.


> Howdy,
>
> I am trying to figure out if there is a different/newer/better(?) way to 
> announce our public IP ranges to our Internet providers, currently we are 
> declaring our subnets in 'network statements' in the BGP configuration, we 
> have static routes setup like ip route x.x.x.x 255.255.224.0 Null0 254 and 
> then we have a extended access-list applied to each peer with our net 
> blocks listed in them.
>
> It appears that because of the network statements, the supernet routes 
> (/18s, /19s, etc) are being distributed via BGP to the rest of the network 
> which is by design(I assume). This doesn't seem ideal because if traffic 
> is sent to an IP address that doesn't have a more specific route than say 
> /18, or /19 it travels all the way through the network to the edge before 
> stopping. I might be blowing the impact of this out of proportion, but it 
> just seems like a waste of resources.
>
> Does anyone know of a seemingly more sensible way of doing this?
>
> -Drew
>
>
>
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