【正文】 tion bgp logneighborchanges neighbor remoteas 1 no autosummary!EndR2!interface Serial1/0 ip address !router bgp 1 no synchronization bgp logneighborchanges neighbor remoteas 1 no autosummary!EndR1sh ip routeCodes: C connected, S static, R RIP, M mobile, B BGP D EIGRP, EX EIGRP external, O OSPF, IA OSPF inter area N1 OSPF NSSA external type 1, N2 OSPF NSSA external type 2 E1 OSPF external type 1, E2 OSPF external type 2 i ISIS, su ISIS summary, L1 ISIS level1, L2 ISIS level2 ia ISIS inter area, * candidate default, U peruser static route o ODR, P periodic downloaded static routeGateway of last resort is not set , 1 subnetsR [120/1] via , 00:00:25, FastEthernet0/0 , 2 subnetsC is directly connected, FastEthernet0/0C is directly connected, Serial1/1作重分發(fā)R1sh ip protocols Routing Protocol is rip Sending updates every 30 seconds, next due in 13 seconds Invalid after 180 seconds, hold down 180, flushed after 240 Outgoing update filter list for all interfaces is not set Ining update filter list for all interfaces is not set Redistributing: rip Default version control: send version 2, receive version 2 Interface Send Recv Triggered RIP Keychain FastEthernet0/0 2 2 Serial1/1 2 2 Automatic network summarization is not in effect Maximum path: 4 Routing for N。所以這里的解決方法就是在R1通過BGP通告網(wǎng)絡給R2 時，因該不改變 下一條，這樣R2 可以直接通過IGP路由表把去往R4 ，這樣環(huán)路就避免了，也避免了次優(yōu)路徑?？梢苑乐弓h(huán)路及次優(yōu)路徑拓撲描述IGP部分R1 R2 R3 R4 使用自己路有器編號創(chuàng)建LOOPBACK 口地址，比如R1 R2 R1 R2 R3 R4 全部啟用OSPF 并且將各自LOOPBACK 口宣告進OSPF BGP部分R1 R3 建立IBGP對等體關(guān)系，R1 R3 BGP AS號為2R4 與R3 建立EBGP對等體關(guān)系。R2sh ip bgp BGP table version is 4, local router ID is Status codes: s suppressed, d damped, h history, * valid, best, i internal, r RIBfailure, S StaleOrigin codes: i IGP, e EGP, ? inplete Network Next Hop Metric LocPrf Weight Path* 100 0 i.（2） 如果給所有的BGP鄰居發(fā)送一條默認路由，那么要完成這個任務我們必須通過三個步驟去完成。 EGP—BGP 知識點200874 CCIE 集訓營 宋濤1: IBGP PEER試驗 22:夸路由器建立IBGP 鄰居 53: EBGP 對等體配置 84:在BGP對等體中制定更新源和對等體地址 11 在IBGP中使用環(huán)回口作為更新源及對等體地址 11 EBGP 建立隊等體關(guān)系時使用環(huán)回口作更新源和隊等體地址 13 網(wǎng)絡通告 15 157:理解IBGP的防環(huán)機制及理解同步原則 188：nexthopself 和 nexthopunchanged 講解 22 解釋 22 NEXTHOPUNCHANGED解釋 229:理解BGP 自動匯總 26 BGP基本的匯總概念 27 重分發(fā)時的自動匯總 2910：BGP路由優(yōu)選特性 33:本地優(yōu)先級影響出站策略試驗 33:MED影響進站策略試驗 42 WEIGHT 影響路由出站試驗 43 影響選路 43 BGP 后門路由特性 44 路由抑制 4411:BGP匯總試驗 46 簡單的匯總試驗 4611．2 匯總后限制明細路由被發(fā)送 47 匯總時的ASPATH信息丟失 49 防止BGP匯總時丟失路徑信息 49 匯總時作路由屬性修改 53 匯總路有的路由抑制試驗 55 BGP 匯總的通告映射 5712: BGP團隊屬性 63 公認的團體屬性設置 63 自定義團體屬性 6415：BGP 路由過濾 67 routemap 過濾 67 distributelist 過濾 67 prefixlist 前綴列表過濾 67 filterlist 6816:BGP 路由反射器 70 試驗拓撲 70 試驗目的 70 配置步驟 7117：對等體組 72 試驗拓撲 72 試驗需求 72 配置命令 7218:過濾專用AS 7319：聯(lián)盟 74 試驗拓撲 74 試驗需求 74 配置命令 7520:CCIE 考試中的LOCALAS 和ALLOWIN參數(shù) 76 試驗拓撲 76 試驗需求 76Bgp basic configurationStep 1 啟用BGPRouter bgp xxStep 2 關(guān)閉自動匯總No autosummaryStep 3 配置ROUTERIDBgp routerid Step 4 指定對等體Neighbor remoteas xx這個地址是對等體地址，該地址必須可達Neighbor updatesource loopback xx指明OPEN 和UPDATA 消息的更新源地址是當前設備哪個接口Neighbor multiplehop xx //當和PEER 建立EBGP PEER 關(guān)系時，如果是非直連用該命令進行TTL 的修改。（1） 如果只給特定的對端通告默認路由，那么可以通過neighbor defaultoriginate命令完成，使用這條命令時，不管本地的路由表中有沒有默認路由都可以實現(xiàn)。network R1sh ip bgp BGP table version is 2, local router ID is Status codes: s suppressed, d damped, h history, * valid, best, i internal, r RIBfailure, S StaleOrigin codes: i IGP, e EGP, ? inplete Network Next Hop Metric LocPrf Weight Path* 0 32768 iR2sh ip bgp BGP table version is 10, local router ID is Status codes: s suppressed, d damped, h history, * valid, best, i internal, r RIBfailure, S StaleOrigin codes: i IGP, e EGP, ? inplete Network Next Hop Metric LocPrf Weight Path* 100 0 iR3sh ip bgp BGP table version is 7, local router ID is Status codes: s suppressed, d damped, h history, * valid, best, i internal, r RIBfailure, S StaleOrigin codes: i IGP, e EGP, ? inplete Network Next Hop Metric LocPrf Weight Path* 0 0 1R3sh ip routeCodes: C connected, S static, R RIP, M mobile, B BGP D EIGRP, EX EIGRP external, O OSPF, IA OSPF inter area N1 OSPF NSSA external type 1, N2 OSPF NSSA external type 2 E1 OSPF external type 1, E2 OSPF external type 2 i ISIS, su ISIS summary, L1 ISIS level1, L2 ISIS level2 ia ISIS inter area, * candidate default, U peruser static route o ODR, P periodic downloaded static routeGateway of last resort is to network , 2 subnetsC is directly connected, Serial1/0S is directly connected, Serial1/0B* [20/0] via , 00:02:117:理解IBGP的防環(huán)機制及理解同步原則從IBGP學習路由時必須考慮的下一條可達IGp路由表同步(同步原則)R1router bgp 2 no synchronization bgp logneighborchanges network mask neighbor remoteas 1 no autosummaryR2!router bgp 1 no synchronization bgp logneighborchanges network mask neighbor remoteas 1 neighbor remoteas 2 no autosummary!R3!router bgp 1 no synchronization bgp logneighborchanges neighbor remoteas 1 no autosummary! R2 BGP轉(zhuǎn)發(fā)表和路由表里的情況R1sh ip bgp BGP table version is 3, local router I