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Re: Open Source BGP Route Optimization?

  • From: Sam Stickland
  • Date: Sat May 29 06:36:03 2004

Per Gregers Bilse <bilse@networksignature.com> wrote:
> On May 28, 10:37am, "Sam Stickland" <sam_ml@spacething.org> wrote:
>> Are there any BGP extensions that would cause a BGP speaker to
>> foward all of it's paths, not just it best? I believe quagga had
>> made some recent attempts
>
> It has been discussed and been on wish lists, but:
>
>> in this direction. IIRC the problem isn't to do with the route
>> annoucements, it's the route withdrawals. I believe BGP only
>> specifies the prefix being withdrawn and not the path, so if it's
>> advertised multiple paths to a prefix it's impossible to know which
>> has been withdrawn.
>
> That is 100% correct, yes.  Selective withdrawal is not supported.
>
> Another issue is that there isn't much point, as far as regular BGP
> and routing considerations go.  Whichever is the best path for a
> border router is the best path; telling other routers about paths it
> will not use serves no (or at best very little) point in this context.

Well something came up recently on a transit router. It takes multiple
Tier-1 feeds, but management wanted to sell a just MFN to a customer. It's
possible to policy route all of their traffic to the MFN interface and only
advertise their prefixes to MFN, but not possible to only feed them the MFN
routes without starting to use VRFs etc.

Of course this is a great perversion of resources ;)

Sam






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