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1、Cisco Confidential 2010 Cisco and/or its affiliates. All rights reserved. 1 BGP技术：路由反射器 Ender.joe(周亚军 ) RS CCIE,SP CCIE,思科认证讲师 #34708 RS & SP CCIE讲师， Yeslab（上 海） Ender BGP v3.2 6-2 Scaling Service Provider Networks Introducing Route Reflectors 2012 Cisco and/or its affiliates. All rights reserved. C
2、isco Confidential 3 Overview IBGP Scalability Issues in a Transit AS-RR在一个大型传输网络的作用 Route Reflector Split-Horizon Rules-RR的水平分割原则 Redundant Route Reflectors-冗余的 RR Route Reflector Clusters-RR簇 Additional Route Reflector Loop-Prevention Mechanisms-RR的防环机制 Summary 2012 Cisco and/or its affiliates. All
3、 rights reserved. Cisco Confidential 4 IBGP requires a full mesh between all BGP-speaking routers. Large number of TCP sessions Unnecessary duplicate routing traffic Solutions Route reflectors modify IBGP split-horizon rules（ RR修改了 IBGP的水平分割原则） BGP confederations modify IBGP AS-path processing（ BGP联
4、邦修改了 IBGP的 AS-path） 2012 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 5 Classic IBGP: IBGP routes are not propagated to other IBGP peers. Full mesh of IBGP peers is therefore required. Route reflector can propagate IBGP routes to other IBGP peers（ RR通告 IBGP路由给其他 IBGP peer） Fu
5、ll mesh of IBGP peers is no longer required（全互联不再需要） 2012 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 6 1、从 EBGP收到的通告给所有的内部邻居 2、从一个 RR的客户端收到的路由通告给其他所有邻居（包括客户端和非客户端） 2012 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 7 3、从一个非客户端的 IBGP邻居收到的路由会发送给客户端和 EBG
6、P邻居 4、所有 IBGP和 EBGP路由发送给 EBGP邻居 2012 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 8 RR必须设计成为冗余的，否则会成为单点故障点 2012 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 9 冗余的 RR解决了高可用性问题 Originator-ID是在 AS边界得到路由时的一个标识（当路由经过 R1-R2-R3传递回来时拒收） Cluster-ID，当 R2和R3的 clu
7、ster-ID相同时 ，R3不再接收 R2反射来的路由 簇的概念用于在 RR之间阻止环路 R1 R2 R3 2012 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 10 A group of redundant route reflectors and their clients form a cluster-冗余的 RR和他们的客户端形成一个簇 Each cluster must have a unique cluster-ID-每个簇有一个单独的cluster-ID Each time a rout
8、e is reflected, the cluster-ID is added to the cluster-list BGP attribute-当路由被反射时，会在 BGP的 cluster-list属性中增加cluster-ID The route that already contains the local cluster-ID in the cluster-list is not reflected-收到的路由已经包含了本身的 cluster-ID将不会接收 2012 Cisco and/or its affiliates. All rights reserved. Cisco C
9、onfidential 11 路由被拒 收 因为 cluster-id已经包含在 cluster-list中 2012 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 12 Every time a route is reflected, the router-ID of the originating IBGP router is stored in the originator-ID BGP attribute.一条路由被反射时，起源的 iBGP路由器的 RID会被收集为 originator-ID属
10、性 A router receiving an IBGP route with originator-ID set to its own router-ID ignores that route.当收到一个 originator-ID和本路由器的RID一致时忽略该路由 The BGP path selection procedure is modified to take into account cluster-list and originator-ID-第 11条和第 12条选路原则被修改 2012 Cisco and/or its affiliates. All rights rese
11、rved. Cisco Confidential 13 Configure cluster-ID on route reflectors. Configure BGP neighbors as route reflector clients on the route reflectors. No configuration is needed on the route reflector clients. 2012 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 14 bgp cluster-id clu
12、ster-id router(config-router)# Optionally assigns a cluster-ID to the route reflector (default value is router-ID) Required only for clusters with redundant reflectors Cluster-ID cannot be changed after the first client is configured neighbor ip-address route-reflector-client router(config-router)#
13、Configures an IBGP neighbor to be a client of this reflector 2012 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 15 2012 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 16 show ip bgp neighbors router# Displays whether a neighbor is a route reflector client
14、 show ip bgp network mask router# Displays additional path attributes (originator-ID and cluster-list) 2012 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 17 2012 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 18 Routes received from the client as seen on
15、the reflector Reflected routes as seen on the client 2012 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 19 BGP route reflectors were introduced to free the network designers from IBGP full-mesh requirements that prevent large networks from scaling. BGP route reflectors modify
16、IBGP split-horizon rules in that all routes that are received from a route reflector client are sent to all other IBGP neighbors, and all routes that are received from a nonclient IBGP neighbor are sent to all route reflector clients. A route reflector is a single point of failure, and therefore redundancy should be impleme
