文档介绍：BGP 102:Scaling workAvi AccessIntroduction?BGP is relatively easy to get configured and basically announcing and using routes.?It is difficult to scale to the tens-to-hundreds of routers scale with full iBGP mesh, AS-Path filters, and AS-Path padding as the only tools.?We munities, Confederations, and local-pref use, and some other features, and show them used in (1)?Review basic BGP concepts?Simple BGP Scaling concepts–Inserting BGP Routes–Stable Routing and Scaling w/ Loopbacks–Save CPU and Typing w/ Peer-Groups–Meaningful MEDsTopics (2)?Scalable Advertisements munities?Scalable Route-Selection with local-prefs?iBGP Scaling Issues?BGP Confederations?BGP Scaling with ConfederationsTopics (3)?Supporting Multi-Homed Customers?Backup Transit?work - Topology?work - Design Goals?work - Implementation?Review Router ConfigurationBGP Concept ReviewBGP Intro?BGP4 is the protocol used on the to exchange routing information between providers, and to propagate external routing information works.?Each work is called an Autonomous System.?ASs which inject routing information on their own behalf have Peering?BGP-speaking routers peer with each other over TCP sessions, and exchange routes through the peering sessions.?Providers typically try to peer at multiple places. Either by peering with the same AS multiple times, or because some ASs are multi-homed, a work will have many candidate paths to a given BGP Route?The BGP route is, conceptually, a “promise” to carry data to a section of IP space. The route is a “bag” of attributes.?The section of IP space is called the “prefix” attribute of the route.?As a BGP route travels from AS to AS, the ASN of each AS is stamped on it when it leaves that AS. Called the AS_PATH attribute, or “as-path” in Cisco- Route Attributes?In addition to the prefix, the as-path, and the next-hop, the BGP route has other attributes, affectionately known as “knobs and twiddles”-–weight, rarely used - “s