[c-nsp] eBGP --> OSPF --> eBGP vs eBGP --> iBGP --> eBGP

[Joe Provo]

On Mon, Apr 27, 2009 at 02:05:17PM -0400, Adam Greene wrote:
> Hi,
> 
> We run BGP to our upstream providers and OSPF on our local backbone. 
> 
> We have a customer who will be multihomed and needs us to advertise his IP blocks to us via BGP. 
> 
> My question is how best to propagate his AS-PATH prepending to
> my upstream providers. Is it possible to inject this information
> into OSPF and then into the eBGP to my upstreams? 

Possible yes, but full of fail.

> Or should I plan on establishing iBGP sessions between the backbone 
> router that will be servicing the customer and the routers facing 
> my upstream providers? I assume the latter ....

Yes.  For maximal win along the axes (scalable,flexible,maintainable),
your OSPF should only carry only loopbacks and network edges (just 
enough to enable next-hop processing of BGP) and your iBGP should 
carry all the prefixes.

Cheers!

Joe

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