BGP路由策略与选路控制.doc

wordBGP路由策略与选路控制1、 实验目标：根据BGP路由选择原如此，用BGP属性控制BGP路由2、 网络拓扑图：3、 配置：IP地址如下列图用OSPF实现IGP路由可达BGP配置如下：no synchronization No auto-summary Update-source lo0 Next-hop-self R3和R4为同簇路由反射器，R1,R2分别为R3和R4的客户端 R3，R4建立普通IBGP邻居 R1与R5，R2与R6建立EBGP现分析下面路由RT1#show ip bgp Network Next Hop Metric LocPrf Weight Path*> 10.0.15.2 0 0 65001 i*> 10.0.15.2 0 0 65001 i根据EBGP路由优先于IBGP路由BGP routing table entry for 10.5.0.0/16, version 11Paths: (2 available, best #2, table Default-IP-Routing-Table) Advertised to update-groups: 2 65001 10.0.0.2 (metric 101) from 10.0.0.4 (10.0.0.4) Origin IGP, metric 0, localpref 100, valid, internal 65001 10.0.15.2 from (10.5.0.1) Origin IGP, metric 0, localpref 100, valid, external, bestRT2#show ip bgp R2同R1 Network Next Hop Metric LocPrf Weight Path* i 10.0.0.1 0 100 0 65001 i* i 10.0.0.1 0 100 0 65001 iBGP routing table entry for 10.5.0.0/16, version 10Paths: (2 available, best #1, table Default-IP-Routing-Table) Advertised to update-groups: 2 65001 10.0.26.2 from (10.6.0.1) Origin IGP, metric 0, localpref 100, valid, external, best 65001 10.0.0.1 (metric 101) from 10.0.0.3 (10.0.0.3) Origin IGP, metric 0, localpref 100, valid, internalRT3#show ip bgp Network Next Hop Metric LocPrf Weight Path* i 10.0.0.2 0 100 0 65001 i*>i 10.0.0.1 0 100 0 65001 i* i 10.0.0.2 0 100 0 65001 i*>i 10.0.0.1 0 100 0 65001 i根据到达下一跳IGP开销小的BGP routing table entry for 10.5.0.0/16, version 18Paths: (3 available, best #3, table Default-IP-Routing-Table) Advertised to update-groups: 1 2 65001, (Received from a RR-client) 10.0.0.2 (metric 201) from Origin IGP, metric 0, localpref 100, valid, internal 65001 10.0.0.2 (metric 201) from 10.0.0.4 (10.0.0.4) Origin IGP, metric 0, localpref 100, valid, internalOriginator: 10.0.0.2, Cluster list: 10.0.0.4 10.0.0.4反射得来，只反射最优路由 65001, (Received from a RR-client) 10.0.0.1 (metric 101) from Origin IGP, metric 0, localpref 100, valid, internal, best注：R3上该路由的最优路由来自RT1，所以不会反射回给RT1 同理，RT4不会反射给RT2RT4#show ip bgp R4同R3 Network Next Hop Metric LocPrf Weight Path* i 10.0.0.1 0 100 0 65001 i* i 10.0.0.1 0 100 0 65001 i* i 10.0.0.1 0 100 0 65001 i* i 10.0.0.1 0 100 0 65001 iRT4#show ip bgp 10.5.0.0 BGP routing table entry for 10.5.0.0/16, version 8Paths: (3 available, best #1, table Default-IP-Routing-Table) Advertised to update-groups: 1 2 65001, (Received from a RR-client) 10.0.0.2 (metric 101) from 10.0.0.2 (10.0.0.2) Origin IGP, metric 0, localpref 100, valid, internal, best 6500110.0.0.1 (metric 201) from 10.0.0.3 (10.0.0.3) Origin IGP, metric 0, localpref 100, valid, internal 65001, (Received from a RR-client) 10.0.0.1 (metric 201) from 10.0.0.1 (10.0.0.1) Origin IGP, metric 0, localpref 100, valid, internalR5、R6选路根据EBGP路由优先于IBGP路由RT5#show ip bgp Network Next Hop Metric LocPrf Weight Path*> 10.0.15.1 0 65000 i*> 10.0.15.1 0 65000 i*> 10.0.15.1 0 65000 i*> 10.0.15.1 0 65000 iRT6#show ip bgp Network Next Hop Metric LocPrf Weight Path*> 10.0.26.1 0 65000 i*> 10.0.26.1 0 65000 i*> 10.0.26.1 0 65000 i*> 10.0.26.1 0 65000 i现将R3,R4参加到同一个簇，这样R3不会反射给R4，R4也不会反射给R3因为Cluster list同为10.0.0.3，防环RT4(config)#router bgp 65000RT4#show ip bgp Network Next Hop Metric LocPrf Weight Path* i 10.0.0.1 0 100 0 65001 i* i 10.0.0.1 0 100 0 65001 i方案一：调节本地优先级本地优先级 local-preference默认为100，越大越优先，调节 local-preference控制路由将RT1从RT5收到的10.5.0.0/16路由本地优先级设为300，大于RT2的100将RT2从RT6收到的10.6.0.0/16路由本地优先级设为300，大于RT1的100RT1(config)#RT1(config)#route-map rt1 permit 10 RT1(config-route-map)#match ip address prefix-list p3RT1(config-route-map)#set local-preference 300 设置该路由优先级为300RT1(config)#route-map rt1 permit 20 覆盖route-map的隐含拒绝RT1(config)#router bgp 65000RT1(config-router)#RT2(config)#RT2(config)#route-map rt2 permit 10RT2(config-route-map)#match ip address prefix-list p3RT2(config-route-map)#set local-preference 300RT2(config)#route-map rt2 permit 20RT2(config)#router bgp 65000RT2(config-router)#neighbor 10.0.26.2 route-map rt2 inRT1#clear ip bgp *RT2#clear ip bgp * 必须要去除BGP邻居重新建立RT1#show ip bgp Network Next Hop Metric LocPrf Weight Path* i 10.0.0.2 0 300 0 65001 i* 10.0.15.2 0 0 65001 iLocPrf为300，来自EBGPLocPrf为300，来自R2，优于来自RT2#show ip bgp Network Next Hop Metric LocPrf Weight Path* i 10.0.0.1 0 300 0 65001 i* 10.0.26.2 0 0 65001 iLocPrf为300，EBGP10.0.26.2 RT3#show ip bgp Network Next Hop Metric LocPrf Weight PathRT4#show ip bgp方案二：调节MEDBGP路由默认MED值为0，越小越优先RT1(config)#route-map med permit 10 RT1(config-route-map)#match ip add prefix-list bluefoxRT1(config-route-map)#set metric 789 设置MED RT1(config)#route-map med permit 20 覆盖隐含拒绝RT1(config)#router bgp 65000RT1(config-router)#neighbor 10.0.15.2 route-map med out 运用于邻居10.0.15.2 OUT方向RT2(config)#RT2(config)#route-map med permit 10RT2(config-route-map)#match ip address prefix-list bluefoxRT2(config-route-map)#set metric 666RT2(config)#route-map med permit 20RT2(config)#router bgp 65000RT2(config-router)#neighbor 10.0.26.2 route-map med out RT5#show ip bgp Network Next Hop Metric LocPrf Weight Path* 10.0.15.1 789 0 65000 i MED为789* 10.0.15.1 789 0 65000 iRT6#show ip bgp Network Next Hop Metric LocPrf Weight Path*>i 10.5.0.1 0 100 0 65000 i方案三：增加ASRT1(config)#route-map as permit 10RT1(config-route-map)#match ip address prefix-list bluefoxRT1(config-route-map)#set as-path prepend 65000 65000 65000 增as-pathRT1(config)#route-map as permit 20RT1(config)#router bgp 65000RT1(config-router)#neighbor 10.0.15.2 route-map as out RT2(config)#RT2(config)#route-map as permit 10RT2(config-route-map)#match ip address prefix-list bluefox RT2(config-route-map)#set as-path prepend 65000 65000RT2(config)#route-map as permit 20RT2(config)#router bgp 65000RT2(config-router)#neighbor 10.0.26.2 route-map as outRT5#show ip bgp Network Next Hop Metric LocPrf Weight Path* 10.0.15.1 0 65000 65000 65000 65000 i* 10.0.15.1 0 65000 65000 65000 65000 iRT6#show ip bgp Network Next Hop Metric LocPrf Weight Path* 10.0.26.1 0 65000 65000 65000 i4、 总结：配置完成是刚刚开始分析每一条路由怎么来的，根据网络需要控制路由选路，熟练掌握路由策略的工具分析链路故障会出现什么问题，如何解决8 / 8