[c-nsp] BGP path preference

[Andy Dills]

On Tue, 28 Aug 2007, Justin Shore wrote:

> Does anyone have any suggestions on how to work around this?  L3 will 
> eventually fix it when they eliminate 19094 but who knows when that will 
> be.  I thought about trying to use a regex to match "19094 3356" to 
> raise local pref even higher.  I also see plenty of routes that from 
> 3356 directly to 22773 (L3 peering w/ Cox wo/ Telcove in the middle).  I 
> could try to match routes that originate on 3356 and 19094 and raise the 
> local pref of those prefixes.  Do I need to raise it on one AND lower it 
> on the other border router or would doing it on one suffice and be 
> manageable?  Would this regex matching be a good best (better?) practice 
> for all circuits over matching an ACL or prefix-list of prefixes?  If so 
> would one match on origin or simply if the ASN was in the path?

Don't forget that you can prepend incoming announcements as well as 
outgoing announcements.

For instance, to account for the fact that there is essentially an 
extra AS in your transit path to 3356, you might just prepend a 
single 22773 to everything Cox announces you.

You might find that to be a more useful tool in this scenario than the 
heavy-handed localpref and weights.

Andy

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Andy Dills
Xecunet, Inc.
www.xecu.net
301-682-9972
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