BGP路由策略与选路控制

1、BGP路由策略与选路限制一、实验目标：根据BGP路由选择原那么,用 BGP属性限制BGP路由网络拓扑图:10. 6 1.10/301.1/30 n AS 6BOOQS0/1IC. 0. 15. 1/3010.0. Z6,1Z30ICPx OSPF 1 工re改 白、in/nkTSTTvSq110.0. 0,4/3210.3. 11/24 E370 L0：ia 110一3拉里I：EBGP10. 6.610. 5.1, 2/3010. S. S. 1/24 Wu以电诅J/3Q普通 1EGP AS BSDOl三、配置：IP地址如下图用OSPF实现IGP路由可达BGP 配置如下：no synchron

2、izationNo auto-summaryUpdate-source lo0Next-hop-selfR3和R4为同簇路由反射器,R1,R2分别为R3和R4的客户端R3, R4建立普通旧GP邻居BGPR3, R4 都发布 10.0.0.0/16, 10.2.0.0/16, 10.4.0.0/16, 10.3.0.0/16R5, R6 发布 10.5.0.0/16, 10.6.0.0/16 至U BGPR1 与 R5, R2 与 R6 建立 EBGP现分析下面路由Metric LocPrf Weight Path 01000 65001 i00 65001 i01000 65001 i00 6

3、5001 iRT1#show ip bgpNetworkNext Hop* i10.5.0.0/1610.0.0.2* >10.0.15.2* i10.6.0.0/1610.0.0.2* >10.0.15.2根据EBGP路由优先于 旧GP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:26500110.

4、0.0.2 (metric 101) 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来自 IBGP10.0.0.4 反射的路由6500110.0.15.2 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, bestMetric LocPrf Weight P

5、ath 00 65001 i01000 65001 i00 65001 i01000 65001 i10RT2#show ip bgp R2 同 R1NetworkNext Hop* > 10.5.0.0/1610.0.26.2* i10.0.0.1* > 10.6.0.0/1610.0.26.2* i10.0.0.1RT2#show ip bgp 10.5.0.0BGP routing table entry for 10.5.0.0/16,Paths: (2 available, best #1, table Default-IP-Routing-Table)Advertise

6、d to update-groups:6500110.0.26.2 from 10.0.26.2 (10.6.0.1)Origin IGP, metric 0, localpref 100, valid, external, best6500110.0.0.1 (metric 101) from 10.0.0.3 (10.0.0.3)Origin IGP, metric 0, localpref 100, valid, internalOriginator: 10.0.0.1, Cluster list: 10.0.0.3RT3#show ip bgpNetwork* i10.5.0.0/16

7、* i*>i* i10.6.0.0/16* i*>i根据到达下一跳Next Hop10.0.0.210.0.0.210.0.0.110.0.0.210.0.0.210.0.0.1IGP开销小的Metric LocPrf Weight Path0100010001000100010001000 65001 i0 65001 i0 65001 i0 65001 i0 65001 i0 65001 iRT3#show ip bgp 10.5.0.0BGP routing table entry for 10.5.0.0/16, version 18Paths: (3 available,

8、 best #3, table Default-IP-Routing-Table)Advertised to update-groups:1 265001, (Received from a RR-client)10.0.0.2 (metric 201) from 10.0.0.2 (10.0.0.2) 来自 IBGP10.0.0.2Origin IGP, metric 0, localpref 100, valid, internal6500110.0.0.2 (metric 201) from 10.0.0.4 (10.0.0.4)Origin IGP, metric 0, localpr

9、ef 100, valid, internalOriginator: 10.0.0.2, Cluster list: 10.0.0.410.0.0.4 反射得来,只反射最正确路由65001, (Received from a RR-client)10.0.0.1 (metric 101) from 10.0.0.1 (10.0.0.1) 来自 IBGP10.0.0.1Origin IGP, metric 0, localpref 100, valid, internal, best 注：R3上该路由的最正确路由来自RT1,所以不会反射回给RT1同理,RT4不会反射给RT2RT4#show ip

10、 bgpNetworkR4 同 R3Next Hop*>i10.5.0.0/1610.0.0.201000 65001 i* i10.0.0.101000 65001* i10.0.0.101000 65001*>i10.6.0.0/1610.0.0.201000 65001 i* i10.0.0.101000 65001* i10.0.0.101000 65001Metric LocPrf Weight PathiiiiRT4#show ip bgp 10.5.0.0BGP routing table entry for 10.5.0.0/16, version 8Paths:

11、(3 available, best #1, table Default-IP-Routing-Table)Advertised to update-groups: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, best6500110.0.0.1 (metric 201) from 10.0.0.3 (10.0.0.3)Origin IGP, metric 0, localpr

12、ef 100, valid, internalOriginator: 10.0.0.1, Cluster list: 10.0.0.365001, (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选路本据 EBGP路由优先于 旧GP路由RT5#show ip bgpNetworkNext HopMetric LocPrf Weight Path* i10.0.0.0/1610.6.0.

13、101000 65000 i*>10.0.15.10 65000 i* i10.2.0.0/1610.6.0.101000 65000 i*>10.0.15.10 65000 i* i10.3.0.0/1610.6.0.101000 65000 i*>10.0.15.10 65000 i* i10.4.0.0/1610.6.0.101000 65000 i*>10.0.15.10 65000 iRT6#show ip bgpNetworkNext HopMetric LocPrf Weight Path* i10.0.0.0/1610.5.0.101000 65000

14、i*>10.0.26.10 65000 i* i10.2.0.0/1610.5.0.101000 65000 i*>10.0.26.10 65000 i* i10.3.0.0/1610.5.0.101000 65000 i*>10.0.26.10 65000 i* i10.4.0.0/1610.5.0.101000 65000 i*>10.0.26.10 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由于 Cluster list 同为 10.0.0.3,防环RT4(config)#router bgp 65000RT4(

15、config-router)#bgp cluster-id 10.0.0.3RT4#show ip bgpNetworkNext HopMetric LocPrf Weight Path*>i10.5.0.0/1610.0.0.201000 65001 i* i10.0.0.101000 65001*>i10.6.0.0/1610.0.0.201000 65001 i* i10.0.0.101000 65001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限制路由300,大于 RT2 的 100300

16、,大于 RT1 的 100将RT1从RT5收到的10.5.0.0/16路由本地优先级设为将RT2从RT6收到的10.6.0.0/16路由本地优先级设为RT1(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 10RT1(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(co

17、nfig)# 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-

18、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 bgpNetworkNext Hop*> 10.5.0.0/1610.0.15.2*>i10.6.0.0/1610.0

19、.0.2* i10.0.0.2* 10.0.15.210.5.0.0/16 的 LocPrf 为 300,来自10.6.0.0/16 的 LocPrf 为 300,来自Metric LocPrf Weight Path03000 65001 i03000 65001 i03000 6500100 65001EBGP10.0.15.2R2,优于来自10.0.15.2的该路由0300030000300RT2#show ip bgpNetworkNext Hop*>i10.5.0.0/1610.0.0.1* i10.0.0.1*10.0.26.2*> 10.6.0.0/1610.0.26

20、.2Metric LocPrf Weight Path0 65001 i0 65001 i0 65001 i0 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, EBGP10.0.26.203000 6500103000 6500103000 6500103000 65001Metric LocPrf Weight PathRT3#show ip bgpNetworkNextHop*>i10.5.0.0/1610.0.0.1*>i10.6.0.0/161

21、0.0.0.2RT4#show ip bgp*>i10.5.0.0/1610.0.0.1*>i10.6.0.0/1610.0.0.2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666匹配路由RT1(config)#ip prefix-list bluefox seq 5 permit 10.2.0.0/16RT1(config)#ip prefix-list bluefox seq 10 permi

22、t 10.4.0.0/16RT1(config)#route-map med permit 10RT1(config-route-map)#match ip add prefix-list bluefox设置MED覆盖隐含拒绝运用于邻居10.0.15.2 OUT方向RT1(config-route-map)# set metric 789RT1(config)# route-map med permit 20RT1(config)#router bgp 65000RT1(config-router)# neighbor 10.0.15.2 route-map med outRT2(config

23、)# 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

24、RT5#show ip bgpNetworkNext HopMetric LocPrf Weight Path*>i10.2.0.0/1610.6.0.11000 65000 i10.0.15.17890 65000 i MED为789*> 10.3.0.0/1610.0.15.10 65000 i*>i10.4.0.0/1610.6.0.11000 65000 i10.0.15.17890 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RT6#show ip bgp

25、Network*> 10,2.0.0/16* 10.3.0.0/16*>i*> 10,4,0.0/16Next Hop10.0.26.110.0.26.110.5.0.110.0.26.1Metric LocPrf Weight Path0 65000 i6660 65000 i MDD 为 66601000 65000 i0 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

26、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