BGP路由策略与选路控制.doc

BGP路由策略与选路控制1、 实验目标：根据BGP路由选择原则，用BGP属性控制BGP路由2、 网络拓扑图：3、 配置：IP地址如图所示用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 R3，R4都发布10.0.0.0/16，10.2.0.0/16，10.4.0.0/16，10.3.0.0/16到BGP R5，R6发布10.5.0.0/16，10.6.0.0/16到BGP 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* i10.5.0.0/16 10.0.0.2 0 100 0 65001 i* 10.0.15.2 0 0 65001 i* i10.6.0.0/16 10.0.0.2 0 100 0 65001 i* 10.0.15.2 0 0 65001 i 根据EBGP路由优先于IBGP路由RT1#show ip bgp 10.5.0.0BGP 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 Originator: 10.0.0.2, Cluster list: 10.0.0.4 来自IBGP10.0.0.4反射的路由 65001 10.0.15.2 from 10.0.15.2 (10.5.0.1) 来自EBGP10.0.15.2的路由 Origin IGP, metric 0, localpref 100, valid, external, bestRT2#show ip bgp R2同R1 Network Next Hop Metric LocPrf Weight Path* 10.5.0.0/16 10.0.26.2 0 0 65001 i* i 10.0.0.1 0 100 0 65001 i* 10.6.0.0/16 10.0.26.2 0 0 65001 i* i 10.0.0.1 0 100 0 65001 iRT2#show ip bgp 10.5.0.0BGP 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 10.0.26.2 (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, internal Originator: 10.0.0.1, Cluster list: 10.0.0.3RT3#show ip bgp Network Next Hop Metric LocPrf Weight Path* i10.5.0.0/16 10.0.0.2 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* i10.6.0.0/16 10.0.0.2 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RT3#show ip bgp 10.5.0.0BGP 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 10.0.0.2 (10.0.0.2) 来自IBGP10.0.0.2 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, internal Originator: 10.0.0.2, Cluster list: 10.0.0.4 10.0.0.4反射得来，只反射最佳路由 65001, (Received from a RR-client) 10.0.0.1 (metric 101) from 10.0.0.1 (10.0.0.1) 来自IBGP10.0.0.1 Origin IGP, metric 0, localpref 100, valid, internal, best注：R3上该路由的最佳路由来自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*i10.5.0.0/16 10.0.0.2 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*i10.6.0.0/16 10.0.0.2 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 65001 10.0.0.1 (metric 201) from 10.0.0.3 (10.0.0.3) Origin IGP, metric 0, localpref 100, valid, internal Originator: 10.0.0.1, Cluster list: 10.0.0.3 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* i10.0.0.0/16 10.6.0.1 0 100 0 65000 i* 10.0.15.1 0 65000 i* i10.2.0.0/16 10.6.0.1 0 100 0 65000 i* 10.0.15.1 0 65000 i* i10.3.0.0/16 10.6.0.1 0 100 0 65000 i* 10.0.15.1 0 65000 i* i10.4.0.0/16 10.6.0.1 0 100 0 65000 i* 10.0.15.1 0 65000 iRT6#show ip bgp Network Next Hop Metric LocPrf Weight Path* i10.0.0.0/16 10.5.0.1 0 100 0 65000 i* 10.0.26.1 0 65000 i* i10.2.0.0/16 10.5.0.1 0 100 0 65000 i* 10.0.26.1 0 65000 i* i10.3.0.0/16 10.5.0.1 0 100 0 65000 i* 10.0.26.1 0 65000 i* i10.4.0.0/16 10.5.0.1 0 100 0 65000 i* 10.0.26.1 0 65000 i现将R3,R4加入到同一个簇，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(config-router)#bgp cluster-id 10.0.0.3RT4#show ip bgp Network Next Hop Metric LocPrf Weight Path*i10.5.0.0/16 10.0.0.2 0 100 0 65001 i* i 10.0.0.1 0 100 0 65001 i*i10.6.0.0/16 10.0.0.2 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)#ip prefix-list p3 seq 5 permit 10.5.0.0/16 匹配路由10.5.0.0/16RT1(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)#neighbor 10.0.15.2 route-map rt1 in 运用于来自邻居10.0.15.2的路由RT2(config)#ip prefix-list p3 permit 10.6.0.0/16 匹配路由10.6.0.0/16RT2(config)#route-map rt2 permit 10RT2(config-route-map)#match ip address prefix-list p3RT2(config-route-map)#set local-preference 300 RT2(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 * 必须要清除BGP邻居重新建立RT1#show ip bgp Network Next Hop Metric LocPrf Weight Path* 10.5.0.0/16 10.0.15.2 0 300 0 65001 i *i10.6.0.0/16 10.0.0.2 0 300 0 65001 i* i 10.0.0.2 0 300 0 65001 i* 10.0.15.2 0 0 65001 i10.5.0.0/16的LocPrf为300，来自EBGP10.0.15.210.6.0.0/16的LocPrf为300，来自R2，优于来自10.0.15.2的该路由RT2#show ip bgp Network Next Hop Metric LocPrf Weight Path*i10.5.0.0/16 10.0.0.1 0 300 0 65001 i* i 10.0.0.1 0 300 0 65001 i* 10.0.26.2 0 0 65001 i* 10.6.0.0/16 10.0.26.2 0 300 0 65001 i10.5.0.0/16的LocPrf为300，来自R1，由于来自EBGP10.0.26.2的该条路由10.6.0.0/16的LocPrf为300，EBGP10.0.26.2 RT3#show ip bgp Network Next Hop Metric LocPrf Weight Path*i10.5.0.0/16 10.0.0.1 0 300 0 65001 i*i10.6.0.0/16 10.0.0.2 0 300 0 65001 iRT4#show ip bgp*i10.5.0.0/16 10.0.0.1 0 300 0 65001 i*i10.6.0.0/16 10.0.0.2 0 300 0 65001 i方案二：调节MEDBGP路由默认MED值为0，越小越优先将RT1发给RT5的路由10.2.0.0/16，10.4.0.0/16的MDE值设成789将RT2发给RT5的路由10.3.0.0/16的MDE值设成666RT1(config)#ip prefix-list bluefox seq 5 permit 10.2.0.0/16 匹配路由RT1(config)#ip prefix-list bluefox seq 10 permit 10.4.0.0/16RT1(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)#ip prefix-list bluefox seq 5 permit 10.3.0.0/16RT2(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*i10.2.0.0/16 10.6.0.1 0 100 0 65000 i* 10.0.15.1 789 0 65000 i MED为789* 10.3.0.0/16 10.0.15.1 0 65000 i*i10.4.0.0/16 10.6.0.1 0 100 0 65000 i* 10.0.15.1 789 0 65000 iRT5上路由10.2.0.0/16和10.4.0.0/16来自10.0.15.1的MED为789，没来自10.6.0.1的优先 10.3.0.0/16来自10.0.15.1RT6#show ip bgp Network Next Hop Metric LocPrf Weight Path* 10.2.0.0/16 10.0.26.1 0 65000 i* 10.3.0.0/16 10.0.26.1 666 0 65000 i MDD为666*i 10.5.0.1 0 100 0 65000 i* 10.4.0.0/16 10.0.26.1 0 65000 i方案三：增加AS增加RT1发给RT5的路由10.2.0.0/16，10.4.0.0/16的As-path增加RT2发给RT5的路由10.3.0.0/16的As-pathRT1(config)#ip prefix-list bluefox seq 5 permit 10.2.0.0/16 匹配路由RT1(config)#ip prefix-list bluefox seq 10 permit 10.4.0.0/16RT1(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)#nei