BGP flooding

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So to sum it up you simply can not run into any scaling ceiling with MP-BGP architecture.

Flooding nature of BGP requires all the related entities treat everything, regardless of whether they need it entirely or not.

That is long gone I am afraid ... Hint RFC 4684. Now applicable to more and more AFI/SAFIs. Also from day one of L3VPNs, PEs even if receiving all routes were dropping on inbound (cheap operation) those routes which contained no locally intersecting RTs. Thx, R.