BGP选路原则详解.ppt

bgp路由选路原则详解 v1.0,学习总结，个人见解，如有错误欢迎改正！,学习目标,掌握bgp十三条选路原则的原理 熟练掌握常见的bgp路由选路原则,bgp路由选路原则,1.weight属性,2.local preference属性,3.本地路由始发方式,4.as-path长度,5.origin属性,6.med属性,7.ebgp优于ibgp,8.到达next-hop的代价,9.执行等价负载均衡,10.ebgp路由接收的顺序,11.路由的router-id,12.cluster-list长度,13.配置的bgp peer指定地址,第一条:weight属性,比较原则及配置注意事项: cisco私有,可通过关联route-map方式进行配置,该值无法传递给其他bgp peer,只能在本地使用.携带的weight值越大,则该路由越优先. 本地始发路由的默认值是32768,从其他bgp peer学习过来的路由的默认值是0 虽然weight属性是cisco私有的,但是很多厂商也是内置该属性(但无法显示及修改),这样就保证了本地始发的路由是最优先的,因为本地始发路由的”weight”为32768,从其他bgp peer学习过来的路由的”weight”为0.,第一条:weight属性,实验验证 r2、r3分别通告10.0.0.0给r1 r1将10.0.0.0使用network方式引入bgp,10.0.0.0/8,10.0.0.0/8,10.0.0.0/8,as 1,as 2,r3,r1,r2,ibgp,ebgp,第一条:weight属性,实验验证 r1的bgp表,r1#sh ip bgp bgp table version is 2, local router id is 9.9.0.1 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * i10.0.0.0 9.9.13.3 0 100 0 i * 9.9.12.2 0 0 2 i * 0.0.0.0 0 32768 i,第一条:weight属性,实验验证 r1对bgp peer应用不同的route-map修改所学习路由的weight值,10.0.0.0/8,10.0.0.0/8,10.0.0.0/8,as 1,as 2,r3,r1,r2,ibgp,ebgp,router bgp 1 -r1的路由策略 neighbor 9.9.12.2 route-map from_r2 in route-map from_r2 permit 10 set weight 65535,第一条:weight属性,实验验证 r1的bgp表选路结果,r1#sh ip bgp bgp table version is 7, local router id is 9.9.0.1 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path r i10.0.0.0 9.9.13.3 0 100 0 i r 9.9.12.2 0 65535 2 i r 0.0.0.0 0 32768 i,bgp路由选路原则,1.weight属性,2.local preference属性,3.本地路由始发方式,4.as-path长度,5.origin属性,6.med属性,7.ebgp优于ibgp,8.到达next-hop的代价,9.执行等价负载均衡,10.ebgp路由接收的顺序,11.路由的router-id,12.cluster-list长度,13.配置的bgp peer指定地址,第二条:local preference属性,比较原则及配置注意事项: 值越大,越优先 默认情况下,本地始发的路由的lp为100,从ebgp peer接收的路由的lp为100. local preference属性只能在ibgp peer之间传递,不能在ebgp peer之间传递,如果在ebgp peer之间收到的路由的路径属性中携带了local preference,则会触发notifacation报文,造成会话中断,第二条:local preference属性,比较原则及配置注意事项: local preference通过如下三种方法进行设置: 通过将igp路由引入bgp时关联route-map进行设置 针对ibgp peer应用in/out方向的route-map,对从peer接收到的或者通告给peer的所有或部分路由进行设置 针对ebgp peer应用in方向的route-map,对从peer接收到的所有或部分路由进行设置 local preference为bgp选路策略中经常使用的一个路径属性,第二条:local preference属性,实验一:local prefenerce无法在ebgp peer之间传递,r1,r2,as 1,as 2,10.0.0.0/8,ebgp,router bgp 2 network 10.0.0.0 neighbor 9.9.12.1 remote-as 1 neighbor 9.9.12.1 route-map to_r1 out ! route-map to_r1 permit 10 set local-preference 500,第二条:local preference属性,实验一:local prefenerce无法在ebgp peer之间传递 查看本地始发的bgp路由的lp值,r2#show ip bgp bgp table version is 2, local router id is 9.9.0.2 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * 10.0.0.0 0.0.0.0 0 32768 i,空值?,r2#sh ip b 10.0.0.0 bgp routing table entry for 10.0.0.0/8, version 2 paths: (1 available, best #1, table default-ip-routing-table) advertised to non peer-group peers: 9.9.12.1 local 0.0.0.0 from 0.0.0.0 (9.9.0.2) origin igp, metric 0, localpref 100, weight 32768, valid, sourced, local, best,第二条:local preference属性,实验一:local prefenerce无法在ebgp peer之间传递 r2通告给r1的bgp路由是否携带lp?,r1#sh ip bgp bgp table version is 2, local router id is 9.9.0.1 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * 10.0.0.0 9.9.12.2 0 0 2 i,500没有传递?,r2#sh ip bgp neighbors 9.9.12.1 advertised-routes bgp table version is 2, local router id is 9.9.0.2 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * 10.0.0.0 0.0.0.0 0 32768 i,第二条:local preference属性,实验一:local prefenerce无法在ebgp peer之间传递 r2通告给r1的bgp update报文,r2通告的10.0.0.0/8前缀的路径属性中不包含local preference属性,第二条:local preference属性,实验二:修改本地始发路由的默认lp值,r1,r2,as 1,10.0.0.0/8,ibgp,router bgp 1 -r2的路由策略 bgp default local-preference 500 network 10.0.0.0 neighbor 9.9.12.1 remote-as 1,第二条:local preference属性,实验二:修改本地始发路由的默认lp值,r2#sh ip b bgp table version is 2, local router id is 10.0.0.1 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * 10.0.0.0 0.0.0.0 0 32768 i,空值?,r2#sh ip b 10.0.0.0 bgp routing table entry for 10.0.0.0/8, version 2 paths: (1 available, best #1, table default-ip-routing-table) advertised to non peer-group peers: 9.9.12.1 local 0.0.0.0 from 0.0.0.0 (10.0.0.1) origin igp, metric 0, localpref 500, weight 32768, valid, sourced, local, best,第二条:local preference属性,实验二:修改本地始发路由的默认lp值,r1#sh ip b bgp table version is 4, local router id is 9.9.0.1 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path *i10.0.0.0 9.9.12.2 0 500 0 i,第二条:local preference属性,实验三:将igp中的路由引入bgp时关联route-map设置lp,r1,r2,as 1,10.0.0.0/8,ibgp,router bgp 1 -r2的路由策略 network 10.0.0.0 route-map set_lp neighbor 9.9.12.1 remote-as 1 ! route-map set_lp permit 10 set local-preference 400,第二条:local preference属性,实验三:将igp中的路由引入bgp时关联route-map设置lp,r2#sh ip b bgp table version is 3, local router id is 10.0.0.1 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * 10.0.0.0 0.0.0.0 0 400 32768 i,r1#sh ip b bgp table version is 6, local router id is 9.9.0.1 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path *i10.0.0.0 9.9.12.2 0 400 0 i,第二条:local preference属性,实验四:对ibgp peer应用in/out方向route-map r3单向访问r6的数据流需求 r1r2对r3应用out方向route-map,r1,as 1,r2,r3,r4,r5,r6,as 2,以该方式部署策略,对数据流控制的作用范围,10.0.0.0/8,11.0.0.0/8,ebgp,第二条:local preference属性,实验四:对ibgp peer应用in/out方向route-map r4、r5正常通告r6的路由，r1、r2的bgp表,r1,as 1,r2,r3,r4,r5,r6,as 2,10.0.0.0/8,11.0.0.0/8,ebgp,r1#sh ip bgp network next hop metric locprf weight path * 10.0.0.0 9.9.15.5 0 2 i * 9.9.14.4 0 2 i * 11.0.0.0 9.9.15.5 0 2 i * 9.9.14.4 0 2 i,r2#sh ip bgp network next hop metric locprf weight path * 10.0.0.0 9.9.25.5 0 2 i * 9.9.24.4 0 2 i * 11.0.0 9.9.25.5 0 2 i * 9.9.24.4 0 2 i,ibgp,ibgp,ibgp,ibgp,第二条:local preference属性,实验四:对ibgp peer应用in/out方向route-map r1、r2的路由策略,router bgp 1 -r1的路由策略 neighbor 9.9.13.3 route-map to_r3 out access-list 1 permit 10.0.0.0 access-list 2 permit 11.0.0.0 route-map to_r3 permit 10 match ip address 1 set local-preference 500 route-map to_r3 permit 20 match ip address 2 set local-preference 400,router bgp 1 -r2的路由策略 neighbor 9.9.23.3 route-map to_r3 out access-list 1 permit 10.0.0.0 access-list 2 permit 11.0.0.0 route-map to_r3 permit 10 match ip address 1 set local-preference 400 route-map to_r3 permit 20 match ip address 2 set local-preference 500,r1,as 1,r2,r3,r4,r5,r6,as 2,10.0.0.0/8,11.0.0.0/8,ebgp,ibgp,ibgp,ibgp,ibgp,第二条:local preference属性,实验四:对ibgp peer应用in/out方向route-map r3的路由选路结果,r3#sh ip b bgp table version is 6, local router id is 9.9.0.3 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * i10.0.0.0 9.9.23.2 0 400 0 2 i *i 9.9.13.1 0 500 0 2 i *i11.0.0.0 9.9.23.2 0 500 0 2 i * i 9.9.13.1 0 400 0 2 i,r1,as 1,r2,r3,r4,r5,r6,as 2,10.0.0.0/8,11.0.0.0/8,ebgp,ibgp,ibgp,ibgp,ibgp,第二条:local preference属性,实验四:对ibgp peer应用in/out方向route-map 路由策略结果：r3到r6的实际单向数据流,r1,as 1,r2,r3,r4,r5,r6,as 2,10.0.0.0/8,11.0.0.0/8,ebgp,以该方式部署策略,对数据流控制的作用范围,第二条:local preference属性,实验五:对ebgp peer应用in方向route-map r3单向访问r6的数据流需求 r1r2分别对r4r5应用out方向的route-map,r1,as 1,r2,r3,r4,r5,r6,as 2,以该方式部署策略,对数据流控制的作用范围,10.0.0.0/8,11.0.0.0/8,ebgp,第二条:local preference属性,实验五:对ebgp peer应用in方向route-map r1、r2的路由策略,router bgp 1 -r1的路由策略 neighbor 9.9.14.4 route-map from_r4 in access-list 1 permit 10.0.0.0 route-map from_r4 permit 10 match ip address 1 set local-preference 500 route-map from_r4 permit 20,router bgp 1 -r2的路由策略 neighbor 9.9.25.5 route-map from_r5 in access-list 2 permit 11.0.0.0 route-map from_r5 permit 10 match ip address 2 set local-preference 500 route-map from_r5 permit 20,r1,as 1,r2,r3,r4,r5,r6,as 2,10.0.0.0/8,11.0.0.0/8,ebgp,ibgp,ibgp,ibgp,ibgp,第二条:local preference属性,实验五:对ebgp peer应用in方向route-map r1、r2的bgp表,r1#sh ip bgp network next hop metric locprf weight path * 10.0.0.0 9.9.15.5 0 2 i * 9.9.14.4 500 0 2 i * 11.0.0.0 9.9.14.4 0 2 i * 9.9.15.5 0 2 i,r2#sh ip bgp network next hop metric locprf weight path * 10.0.0.0 9.9.25.5 0 2 i * 9.9.24.4 0 2 i * 11.0.0.0 9.9.25.5 500 0 2 i * 9.9.24.4 0 2 i,r1,as 1,r2,r3,r4,r5,r6,as 2,10.0.0.0/8,11.0.0.0/8,ebgp,ibgp,ibgp,ibgp,ibgp,第二条:local preference属性,实验五:对ebgp peer应用in方向route-map r3的bgp表,r3#sh ip bgp bgp table version is 10, local router id is 9.9.0.3 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * i10.0.0.0 9.9.23.2 0 100 0 2 i *i 9.9.13.1 0 500 0 2 i *i11.0.0.0 9.9.23.2 0 500 0 2 i * i 9.9.13.1 0 100 0 2 i,r1,as 1,r2,r3,r4,r5,r6,as 2,10.0.0.0/8,11.0.0.0/8,ebgp,ibgp,ibgp,ibgp,ibgp,第二条:local preference属性,实验五:对ebgp peer应用in方向route-map 路由策略结果：r3到r6的实际单向数据流,r1,as 1,r2,r3,r4,r5,r6,as 2,10.0.0.0/8,11.0.0.0/8,以该方式部署策略,对数据流控制的作用范围,bgp路由选路原则,1.weight属性,2.local preference属性,3.本地路由始发方式,4.as-path长度,5.origin属性,6.med属性,7.ebgp优于ibgp,8.到达next-hop的代价,9.执行等价负载均衡,10.ebgp路由接收的顺序,11.路由的router-id,12.cluster-list长度,13.配置的bgp peer指定地址,第三条:本地路由始发方式,比较原则及配置注意事项 该比较原则主要是指本地在进入一条igp路由进去bgp表时，使用不同的方式比如network或redistribute等，那么这些方式之间是存在优先顺序的：networkredistributeaggregate 注意，该原则是不会作为bgp路由选路策略的,第三条:本地路由始发方式,实验验证 本地分别以3种方式引入一条路由，如下配置所示,interface loopback1 ip address 3.3.3.3 255.255.255.255 router bgp 1 network 3.3.3.3 mask 255.255.255.255 route-map a aggregate-address 3.3.3.3 255.255.255.255 attribute-map c redistribute connected route-map b route-map a permit 10 set local-preference 200 route-map b permit 10 set local-preference 300 route-map c permit 10 set local-preference 400,第三条:本地路由始发方式,实验验证 本地bgp表中的显示，network方式为第一选择,r3#sh ip bgp bgp table version is 13, local router id is 9.9.0.3 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * 3.3.3.3/32 0.0.0.0 0 200 32768 i,第三条:本地路由始发方式,实验验证 将network 3.3.3.3 mask 255.255.255.255 删除 redistribute方式成为优选,r3#sh ip b bgp table version is 14, local router id is 9.9.0.3 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * 3.3.3.3/32 0.0.0.0 0 300 32768 ?,bgp路由选路原则,1.weight属性,2.local preference属性,3.本地路由始发方式,4.as-path长度,5.origin属性,6.med属性,7.ebgp优于ibgp,8.到达next-hop的代价,9.执行等价负载均衡,10.ebgp路由接收的顺序,11.路由的router-id,12.cluster-list长度,13.配置的bgp peer指定地址,第四条:as-path长度,比较原则及配置注意事项 优选长度小的as-path列表 其他as-path比较原则： 在做聚合路由时，使用as-set后产生的as-path列表中的里的as号长度只算一个as号的长度 在联盟内的as-path列表中的()的as号长度不做计算依据 当向ebgp peer 通告路由时，将自己的as号加在as-path列表的最左端，向ibgp peer通告路由时，不会对as-path列表做任何修改,第四条:as-path长度,比较原则及配置注意事项 修改as-path列表的方法： 可以通过对ebgp peer使用in/out方向的route-map，使用set as-path prepend命令来添加as号。 注意，上述操作只能对ebgp peer，对ibgp peer无法生效。 可以在bgp进程下使用bgp bestpath as-path ignore命令来跳过as-path的长度比较 修改as-path长度可作为bgp选路策略的一种。,第四条:as-path长度,实验一：使用out方向的route-map来修改as-path r3访问r4的单向数据流需求,r1,r2,r3,r4,as1,as2,10.0.0.0/8,以该方式部署策略,对数据流控制的作用范围,第四条:as-path长度,实验一：使用out方向的route-map来修改as-path r1、r2的路由策略(r1保持默认),router bgp 2 -r2的路由策略 neighbor 9.9.23.3 route-map to_r3 out route-map to_r3 permit 10 set as-path prepend 5 5 5,r1,r2,r3,r4,as1,as2,10.0.0.0/8,ibgp,ebgp,ebgp,ibgp,第四条:as-path长度,实验一：使用out方向的route-map来修改as-path r3的bgp表选路结果,r3#sh ip b bgp table version is 2, local router id is 9.9.0.3 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * 10.0.0.0 9.9.23.2 0 2 5 5 5 i * 9.9.13.1 0 2 i,第四条:as-path长度,实验二：使用in方向的route-map来修改as-path r3访问r4的单向数据流需求,r1,r2,r3,r4,as1,as2,10.0.0.0/8,以该方式部署策略,对数据流控制的作用范围,第四条:as-path长度,实验二：使用in方向的route-map来修改as-path r3的路由策略,router bgp 1 -r3的路由策略 neighbor 9.9.23.2 route-map from_r2 in route-map from_r2 permit 10 set as-path prepend 5 5 5,r1,r2,r3,r4,as1,as2,10.0.0.0/8,ibgp,ebgp,ebgp,ibgp,第四条:as-path长度,实验二：使用in方向的route-map来修改as-path r3的bgp表选路结果,r3#sh ip bgp bgp table version is 2, local router id is 9.9.0.3 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * 10.0.0.0 9.9.23.2 0 5 5 5 2 i * 9.9.13.1 0 2 i,不同方向的route-map对于插入的as号的位置是不同的,bgp路由选路原则,1.weight属性,2.local preference属性,3.本地路由始发方式,4.as-path长度,5.origin属性,6.med属性,7.ebgp优于ibgp,8.到达next-hop的代价,9.执行等价负载均衡,10.ebgp路由接收的顺序,11.路由的router-id,12.cluster-list长度,13.配置的bgp peer指定地址,第五条:origin属性,比较原则及配置注意事项 三种不同的origin属性的优先顺序:igpegpincomplete origin属性会一直在bgp路由中携带 origin属性配置方法： 将igp路由引入bgp时关联route-map进行设置 默认情况下，network方式产生的bgp路由的origin属性为igp，而redistribute方式产生的bgp路由的origin属性为“？” 对bgp peer应用in/out方向的route-map进行设置 很少使用设置origin属性作为bgp路由选路策略,第五条:origin属性,实验1：设置origin属性 r1r2r3分别以network方式引入路由，r1r3关联不同的route-map设置不同的origin属性,11.0.0.0/8,13.0.0.0/8,12.0.0.0/8,as 1,as 2,r3,r1,r2,ibgp,ebgp,router bgp 1 -r3的路由策略 network 13.0.0.0 route-map set_origin route-map set_origin permit 10 set origin incomplete,router bgp 1 -r1的路由策略 network 11.0.0.0 route-map set_origin route-map set_origin permit 10 set origin egp,第五条:origin属性,实验1：设置origin属性 r1的bgp表,r1# sh ip bgp bgp table version is 4, local router id is 9.9.0.1 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * 11.0.0.0 0.0.0.0 0 32768 e * 12.0.0.0 9.9.12.2 0 0 2 i *i13.0.0.0 9.9.13.3 0 100 0 ?,第五条:origin属性,实验1：设置origin属性 r1对r3应用in方向的route-map修改origin属性，r2对r1使用out方向的route-map修改origin属性,11.0.0.0/8,13.0.0.0/8,12.0.0.0/8,as 1,as 2,r3,r1,r2,ibgp,ebgp,router bgp 1 -r1的路由策略 neighbor 9.9.13.3 route-map from_r3 in route-map from_r3 permit 10 set origin igp,router bgp 2 -r2的路由策略 neighbor 9.9.12.1 route-map to_r1 out route-map to_r1 permit 10 set origin incomplete,第五条:origin属性,实验1：设置origin属性 r1的bgp表,r1#sh ip bgp bgp table version is 6, local router id is 9.9.0.1 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * 11.0.0.0 0.0.0.0 0 32768 e * 12.0.0.0 9.9.12.2 0 0 2 ? *i13.0.0.0 9.9.13.3 0 100 0 i,第五条:origin属性,实验2：不同origin属性之间的优先顺序,10.0.0.0/8,10.0.0.0/8,as 1,r3,r1,r2,ibgp,ibgp,10.0.0.0/8,r4,ibgp,router bgp 1 -r3的路由策略 network 10.0.0.0 route-map set_origin route-map set_origin permit 10 set origin incomplete,r2仅使用network方式引入10.0.0.0,router bgp 1 -r4的路由策略 network 10.0.0.0 route-map set_origin route-map set_origin permit 10 set origin egp,第五条:origin属性,实验2：不同origin属性之间的优先顺序 r1的bgp表路由选路结果,r1#sh ip bgp bgp table version is 2, local router id is 9.9.0.1 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * i10.0.0.0 9.9.14.4 0 100 0 e * i 9.9.13.3 0 100 0 ? *i 9.9.12.2 0 100 0 i,第五条:origin属性,实验2：不同origin属性之间的优先顺序 断开r1与r2的连接,r1的bgp表路由选路结果,r1#sh ip b bgp table version is 3, local router id is 9.9.0.1 status codes: s suppressed, d damped, h history, * valid, best, i - internal, r rib-failure, s stale origin codes: i - igp, e - egp, ? - incomplete network next hop metric locprf weight path * i10.0.0.0 9.9.14.4 0 10