
図を参照してください。顧客は、単一のCEルータから2つのサービスプロバイダに対して2つのeBGPピアリングを確立しています。顧客は、特定のトラフィックが確実に顧客側に入るようにするためのソリューションを設計するために、アーキテクトを雇いました。
インターフェース g¡g0/0 を介して s ネットワークに接続します。設計者はどのソリューションを設計に含める必要がありますか?
正解:C
Advertising more-specific prefixes toward the preferred service provider is the correct way to influence inbound traffic to enter through a chosen CE interface. BGP inbound path control is indirect: the enterprise cannot set local preference inside remote autonomous systems, and MED is honored only under specific provider policies. The most deterministic option available to the customer is to advertise a longer-prefix route to the preferred provider because Internet and BGP route selection generally prefer the longest matching prefix before BGP path attributes are considered. If the aggregate is advertised to both providers but a more- specific route is advertised to the provider connected to gig0/0, return traffic for that more- specific destination is attracted through that interface. Lowering MED toward the less preferred provider is the opposite of the desired effect. AS-path prepending toward the preferred provider would make that path less attractive. Local preference affects outbound path selection inside the local AS, not inbound traffic from external networks. Reference topics: BGP inbound traffic engineering, longest-prefix match, route aggregation, AS-path prepending, MED, local preference.