hcie ramp s ch06 bgp技術(shù)基礎(chǔ)第6章

目1BGP的基本概 自治系統(tǒng)AS（Autonomous目1BGP的基本概 自治系統(tǒng)AS（Autonomous BGP報(bào)文交互中的角 BGP的路由器號(hào)（Router BGP工作原 BGP的報(bào) BGP狀態(tài) BGP對(duì)等體之間的交互原 BGP引入IGP路 應(yīng) BGP BGP的路由優(yōu)選規(guī)則和負(fù)載分 BGP選擇路由的策 BGP負(fù)載分 BGP技術(shù)基礎(chǔ)配置示 配置BGP的基本功能示 配置BGP與IGP交互示 配置AS_Path過(guò)濾器示 章前能力測(cè)試配置BGP的MED屬性控制路由選擇示 配置BGP的MED屬性控制路由選擇示 AS（AutonomousAS165535，4AS142949672954AS號(hào)BGP分如圖6-1-1BGP按照運(yùn)行方式分為EBGP（External/ExteriorBGP）設(shè)備接收EBGP對(duì)等體發(fā)送的路由時(shí)，會(huì)將帶有本地AS號(hào)的路由丟棄。立全連接。為了解決IBGP對(duì)等體的連接數(shù)量太多的問(wèn)立全連接。為了解決IBGP對(duì)等體的連接數(shù)量太多的問(wèn)題，BGP設(shè)計(jì)了路由反射器BGPBGP報(bào)文交互中分為SpeakerPeer兩種角（Speaker信息，并發(fā)布（Advertise）給其它BGPSpeaker。Peer：相互交換報(bào)Speaker之間互稱(chēng)對(duì)等體（Peer。若干相關(guān)的對(duì)等體可以構(gòu)GroupBGP的路由器號(hào)（RouterBGPRouterID是一個(gè)用于標(biāo)BGP設(shè)備32位的值，通IPv4地址的形式，在BGP會(huì)話(huà)建立時(shí)發(fā)送的Open報(bào)文中攜帶。對(duì)等體之間建BGP會(huì)話(huà)時(shí)BGP設(shè)備都必須有唯一的RouterID，否則對(duì)等體之間不能建立BGP連接。在設(shè)備上選取。缺省BGP選擇設(shè)備Loopback接口IPv4地址作為BGPRouter持原來(lái)RouterIDBGPBGP對(duì)等體的建立、更新和刪除等交互過(guò)程主要有5種報(bào)文、6種狀態(tài)機(jī)和5個(gè)原則BGP的報(bào)BGP對(duì)等體間通過(guò)以下5種報(bào)文進(jìn)行交互，其中Keepalive報(bào)文為周期性發(fā)送為觸發(fā)式發(fā)Open報(bào)文：用于建立BGP對(duì)等體連接。Notification報(bào)文：用于中斷BGP連接。Keepalive報(bào)文：用于保持BGP連接說(shuō)明他AS，則推薦使用IBGP。Route-refresh報(bào)文：用于在改變路由策略后Route-refresh報(bào)文：用于在改變路由策略后請(qǐng)求對(duì)等體重新發(fā)送路由信息。只有路由刷新（Route-refresh）能力的BGP設(shè)備會(huì)發(fā)送和響應(yīng)此報(bào)文BGP狀態(tài)6-2-1所示，BGP對(duì)等體的交互過(guò)程中存6種狀態(tài)機(jī)：空閑狀態(tài)（Idle、連接狀（Connect（Active（OpenSent和連接已建立（Established。在BGP對(duì)等體建立的過(guò)程中，通?？葾ctiveEstablished3個(gè)狀態(tài)是：Idle6-2-1BGP對(duì)等體交互過(guò) 到本設(shè)備Start事件后，BGP才開(kāi)始嘗試和其它BGP對(duì)等體進(jìn)TCP連接，并Connect Connect狀態(tài)下，BGP啟動(dòng)連接重傳定時(shí)器（ConnectRetry等TCP完成連接說(shuō)明Start事件是由一個(gè)操作者配置一個(gè)BGP過(guò)程，或者重置一個(gè)已經(jīng)存在的過(guò)程或者路由器軟件重置過(guò)程引起的任何狀態(tài)中收到Notification報(bào)文或TCP拆鏈通知等Error事件后，BGP都會(huì)轉(zhuǎn)至Idle狀態(tài)續(xù)嘗試和其它BGP對(duì)等體進(jìn)行TCP連接，停留在Connect狀態(tài)。器，并轉(zhuǎn)至OpenSent狀態(tài)；至Connect狀態(tài)。OpenSent狀態(tài)下，BGPOpenOpenIdle和Notification報(bào)文。行狀態(tài)，將保持BGP連接。知對(duì)端，并轉(zhuǎn)至Idle狀態(tài)。BGPEBGPBGP路由，BGPEBGPIBGP對(duì)等體。路由更新時(shí)，BGP設(shè)備只發(fā)送更新的BGP路由。BGPIGPBGPIGPBGPIGP路BGPBGPAS間的路由的路由。為了更好的規(guī)劃網(wǎng)絡(luò)，BGPIGP的路由時(shí)，可以使用路由策略進(jìn)行路由過(guò)濾和路由屬性設(shè)置，也可以設(shè)置MED值指導(dǎo)EBGP對(duì)等體判斷流量進(jìn)入AS時(shí)選路。BGPIGP路由的有效性，Import方式還可以引入靜態(tài)路IGP引入BGP路6-3-1IGP引入BGP6-3-1IGP引入BGPAS100RouterCBGPISISRouterCBGP路由表中存在AS200RouterBRouterBOSPFBGP路由，實(shí)現(xiàn)BGPBGP使用認(rèn)證和GTSM（GeneralizedTTLSecurityMechanism）BGPBGP認(rèn)BGPBGPGTSMIPTTL（time-to-live）值是否在一個(gè)預(yù)先設(shè)置好的特定范圍IBGPTTL254255BGP協(xié)因?yàn)榭刂茖用嫣幚泶罅抗魣?bào)文，導(dǎo)致設(shè)備CPU占用率高，系統(tǒng)異常繁忙。如果使能BGPBGPBGP屬BGPBGP屬andatory須存在于Update報(bào)文中。如果缺少這類(lèi)屬性，路由信息就會(huì)出錯(cuò)。discretionary求必須存在于Update報(bào)文中，即就算缺少這類(lèi)屬性，路由信息也不會(huì)出錯(cuò)。transitive：BGtrasitive：BGP6-5-1BGPOrigin屬3EGPEGPOriginEGP。Incomplete：優(yōu)先級(jí)最低。通過(guò)其他方式學(xué)習(xí)到的路由信息。比如BGP通過(guò)類(lèi)OriginAS_PathNext_HopLocal_PrefMEDCluster_List攜帶本地AS號(hào)的AS_Path列表。BGPSpeakerIBGPUpdate當(dāng)BGPSpeaker將這條路由通告給EBGP對(duì)等體時(shí)，便會(huì)把本地AS編號(hào)添加在知道去目的地址所要經(jīng)過(guò)的AS。離本地AS最近AS號(hào)排在前面，其他AS號(hào)IP地址。通常情況下，Next_Hop為本地與對(duì)端建立BGP鄰居關(guān)系的接口地址。設(shè)置為本地與對(duì)端建立BGP鄰居關(guān)系的接口地址。的設(shè)備通過(guò)不同的IBGP對(duì)等體得到目的地址相同但下一跳不同的多條路由時(shí)，將優(yōu)先選擇Local_PrefLocal_Pref屬性，BGP選路時(shí)將該路由的Local_Pref值按缺省值100來(lái)處理。MED屬M(fèi)ED（Multi-Exit-Discriminator）AS時(shí)的最佳路由，當(dāng)一個(gè)運(yùn)行BGPEBGP對(duì)等體得到目的地址相同但下一跳不同的多條路由時(shí)，在其它條件相同的情況下，將優(yōu)先選擇MED值較小者作為最佳路由。MEDASAS團(tuán)體屬性分為自定義團(tuán)體屬性和公認(rèn)團(tuán)體屬性。公認(rèn)團(tuán)體屬性如表6-5-2所示6-5-2公認(rèn)團(tuán)體屬Originator_ID屬性和Cluster_List屬Originator_ID屬性和Cluster_List屬性用于解決路由反射器場(chǎng)景中的環(huán)路問(wèn)題BGP當(dāng)?shù)竭_(dá)同一目的地存在多條路由時(shí)，BGP依次對(duì)比下列屬性來(lái)選擇路由優(yōu)選協(xié)議首選值（PrefVal）協(xié)議首選值（PrefVal）是華為設(shè)備的特有屬性，該屬性?xún)H在本優(yōu)選本地優(yōu)先級(jí)（Local_Pref）最高的路由如果路由沒(méi)有本地優(yōu)先級(jí)，BGP選路時(shí)將該路由按缺省的本地優(yōu)先級(jí)100來(lái)處優(yōu)選AS路徑（AS_Path）最短的路由依次優(yōu)選Origin類(lèi)型為IGP、EGP、Incomplete的路由依次優(yōu)選EBGP路由、IBGP路由、LocalCross路由、RemoteCross路由。PE上某個(gè)VPN實(shí)例的VPNv4路由的ERT匹配其他VPN實(shí)例的IRT后復(fù)制到該VPN實(shí)例，稱(chēng)為L(zhǎng)ocalCross；從遠(yuǎn)端PE學(xué)習(xí)到的VPNv4ERT匹配某VPN實(shí)例IRT后復(fù)制到該VPN實(shí)例，稱(chēng)為RemoteCross。 優(yōu)選BGP下一IGP度量值（metric） Cluster_List最短的路由說(shuō)明在IGP中，對(duì)到達(dá)同一目的地址的不同路由，IGP根據(jù)本身的路由算法計(jì)算路由的度量值團(tuán)體屬性名團(tuán)體屬性說(shuō)設(shè)備收到具有此屬性的路由后，將不向任何BGP對(duì)等體發(fā)設(shè)備收到具有此屬性的路由后，將不向AS外發(fā)送該路也不向AS內(nèi)其他子AS發(fā)布此路由。BGP負(fù)載分當(dāng)?shù)竭_(dá)同一目的地址存在多條等價(jià)路由時(shí)，可以通過(guò)BGP等價(jià)負(fù)載分擔(dān)實(shí)現(xiàn)均衡流量BGP組網(wǎng)需6-6-1所示，需RouterBGP協(xié)議，RouterA、RouterB之間建連接，RouterB、RouterCRouterD之間建立IBGP全連接6-6-1配置BGP基本組網(wǎng)配置思采用如下的思路配置BGP的基本功能 RouterB、RouterCRouterD間配置IBGP連接說(shuō)明如果路由攜帶Originator_ID屬性，選路過(guò)程中將比較Originator_ID的大?。ú辉俦容^RouterID），并優(yōu)選Originator_ID最小的路由。 #RouterA<RouterA>system-#[RouterB]bgp[RouterB-bgp]router-id[RouterB-bgp]peer9.1.1.2as-number[RouterB-bgp]peer9.1.3.2as-number#RouterC[RouterC]bgp[RouterC-bgp]router-id[RouterC-bgp]peer9.1.3.1as-number[RouterC-bgp]peer9.1.2.2as-number#RouterD[RouterD]bgp[RouterD-bgp]router-id[RouterD-bgp]peer9.1.1.1as-number[RouterD-bgp]peer9.1.2.1as-number#RouterA[RouterA]bgp[RouterA-bgp]router-id[RouterA-bgp]peer200.1.1.1as-number#RouterB[RouterB-bgp]peer200.1.1.2as-number65008#查看BGP對(duì)等體的連接狀態(tài)。[RouterB]displaybgppeerBGPlocalrouterID:LocalASnumber:Totalnumberofpeers:Peersinestablishedstate:VASMsgRcvdMsgSentOutQ444000001444000001 #配置RouterA發(fā)布路由。[RouterA-bgp]ipv4-familyunicast[RouterA-bgp-af-ipv4]network8.0.0.0#RouterA[RouterA]displaybgprouting-BGPLocalrouterIDisStatuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?-incompleteTotalNumberofRoutes:PrefVal00i#RouterB[RouterB]displaybgprouting-BGPLocalrouterIDisStatuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?-incompleteTotalNumberofRoutes:PrefVal00#RouterC[RouterC]displaybgprouting-BGPLocalrouterIDisStatuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?-incompleteTotalNumberofRoutes:PrefVali00 BGPTotalNumberofRoutes:PrefVali00 BGP引入直連#[RouterB-bgp]ipv4-familyunicast#RouterABGP路由表。[RouterA]displaybgprouting-tableBGPLocalrouterIDisStatuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?-incompleteTotalNumberofRoutes:PrefVal00000000#[RouterC]displaybgprouting-BGPLocalrouterIDisStatuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?-incomplete說(shuō)明從路由表可以看出，RouterC雖然學(xué)到了AS65008中的8.0.0.0的路由，但因?yàn)橄乱惶?00.1.1.2不可達(dá)，TotalNumberofRoutes:PrefValiTotalNumberofRoutes:PrefVali00???000000#Ping[RouterC]pingPING8.1.1.1:56databytes,pressCTRL_CtoReplyfrom8.1.1.1:bytes=56Sequence=1ttl=254time=31msReplyfrom8.1.1.1:bytes=56Sequence=2ttl=254time=47msReplyfrom8.1.1.1:bytes=56Sequence=3ttl=254time=31msReplyfrom8.1.1.1:bytes=56Sequence=4ttl=254time=16msReplyfrom8.1.1.1:bytes=56Sequence=5ttl=254time=31ms---8.1.1.1pingstatistics---5packet(s)transmitted5packet(s)0.00%packetround-tripmin/avg/max=16/31/47##ipaddress8.1.1.1255.0.0.0#interface#bgprouter-idipv4-familyunicastnetwork8.0.0.0peer200.1.1.1ipv4-familyunicastnetwork8.0.0.0peer200.1.1.1###interface#interface#interface#bgprouter-idpeer9.1.1.2as-numberpeer9.1.3.2as-number#ipv4-familyunicastimport-routedirectpeer9.1.1.2enablepeer9.1.3.2peer200.1.1.2###interface#interface#interface#bgprouter-idpeer9.1.2.2as-numberipv4-familyunicastpeer9.1.2.2enablepeer9.1.3.1###interface#interface#bgprouter-idpeer9.1.1.1as-numberipv4-familyunicastpeer9.1.1.1enablepeer9.1.2.1#配置BGPIGP交互示配置BGPIGP交互示6-6-2配置BGPIGP#RouterB[RouterB]ospf[RouterB-ospf-1]area[RouterB-ospf-1quitRouterC。[RouterC]ospf1[RouterC-ospf-1]area#RouterA[RouterA]bgp[RouterA-bgp]router-id[RouterA-bgp]peer3.1.1.1as-number[RouterA-bgp-af-ipv4]network8.1.1.0#RouterB[RouterB]bgp[RouterB-bgp]router-id[RouterB-bgp]peer3.1.1.2as-number #[RouterB-bgp]ipv4-familyunicast[RouterB-bgp-af-ipv4]quit[RouterB-bgp]#RouterA[RouterA]displaybgprouting-BGPLocalrouterIDisStatuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?-incompleteTotalNumberofRoutes:PrefVal002000#[RouterB][RouterB-ospf-1]import-route#RouterC[RouterC]displayiprouting-RouteFlags:R-relay,D-downloadtoRoutingTables:Destinations:Routes:RouteFlags:R-relay,D-downloadtoRoutingTables:Destinations:Routes:ProtoPreFlagsDirectDirectDirectDirectDirectDirect0000001DD #RouterB[RouterB]bgp[RouterB-bgp]ipv4-familyunicast#顯示RouterABGP路由表。[RouterA]displaybgprouting-tableBGPLocalrouterIDisStatuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?-incompleteTotalNumberofRoutes:PrefVali000#Ping[RouterA]ping-a8.1.1.1PING9.1.2.1:56databytes,pressCTRL_CtoReplyfrom9.1.2.1:bytes=56Sequence=1ttl=254time=15msReplyfrom9.1.2.1:bytes=56Sequence=2ttl=254time=31msReplyfrom9.1.2.1:bytes=56Sequence=3ttl=254time=47msReplyfrom9.1.2.1:bytes=56Sequence=4ttl=254time=46Replyfrom9.1.2.1:bytes=56Sequence=5ttl=254time=475packet(s)transmitted5packet(s)5packet(s)transmitted5packet(s)0.00%packetround-tripmin/avg/max=15/37/47##interface#interface#bgprouter-idipv4-familyunicastnetwork8.1.1.0peer3.1.1.1###interface#interface#bgprouter-idipv4-familyrouter-idipv4-familyunicastsummaryautomaticimport-routeospf1peer3.1.1.2#ospfarea0.0.0.0network9.1.1.0###interface#interface#ospfareanetwork9.1.1.0network9.1.2.0#AS_Path6-6-3配置AS_Path6-6-3配置AS_Path連路由，使AS之間通過(guò)EBGP連接實(shí)現(xiàn)相互通信。配置EBGP[RouterA]bgp[RouterA-bgp]router-id[RouterA-bgp]peer200.1.2.2as-number[RouterA-bgp]import-route#RouterB[RouterB]bgp[RouterB-bgp]router-id[RouterB-bgp]peer200.1.2.1as-number[RouterB-bgp]peer200.1.3.2as-number30[RouterB-bgp]import-routedirect[RouterB-bgp]quit#RouterC[RouterC]bgp[RouterC-bgp]router-id[RouterC-bgp]peer200.1.3.1as-number20[RouterC-bgp]import-routedirect[RouterC-bgp]quit#[RouterC]bgp[RouterC-bgp]router-id[RouterC-bgp]peer200.1.3.1as-number20[RouterC-bgp]import-routedirect[RouterC-bgp]quit#<RouterB>displaybgprouting-tablepeer200.1.3.2advertised-BGPLocalrouterIDisStatuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?-incompleteTotalNumberofRoutes:PrefVal020200000000<RouterC>displaybgprouting-BGPLocalrouterIDisStatuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?-incompleteTotalNumberofRoutes:PrefVal020????00000000*0000??0000 *0000??0000 表示任何包含AS30AS列表，“.*”表示與任何字符匹配。[RouterB]ipas-path-filterpath-filter1deny[RouterB]ipas-path-filterpath-filter1permit#[RouterB]ipas-path-filterpath-filter2deny[RouterB]ipas-path-filterpath-filter2permit#[RouterB]bgp[RouterB-bgp]peer200.1.2.1as-path-filterpath-filter1export[RouterB-bgp]peer200.1.3.2as-path-filterpath-filter2export[RouterB-bgp]quit4.RouterB<RouterB>displaybgprouting-tablepeer200.1.3.2advertised-BGPLocalrouterIDisStatuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?-incompleteTotalNumberofRoutes:PrefVal0000<RouterC>displaybgprouting-BGPLocalrouterIDisStatuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-Origin:i-IGP,eh-history,i-internal,s-suppressed,S-Origin:i-IGP,e-EGP,?-TotalNumberofRoutes:PrefVal*000000000000??????0000<RouterB>displaybgprouting-tablepeer200.1.2.1advertised-BGPLocalrouterIDisStatuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?-incompleteTotalNumberofRoutes:PrefVal0000<RouterA>displaybgprouting-BGPLocalrouterIDisStatuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?-incompleteTotalNumberofRoutes:PrefVal*00PrefVal*0000000000?????000000?##interface#interface#bgprouter-id#ipv4-familyunicastimport-routedirectpeer200.1.2.2enable###interfaceipaddress200.1.3.1#interface#interface#bgprouter-idpeer200.1.2.1as-numberipv4-familyunicastimport-routedirectpeer200.1.2.1enablepeer200.1.2.1as-path-filterpath-filter1exportpeer200.1.3.2enablepeer200.1.3.2as-path-filterpath-filter2#ipas-path-filterpath-filter1deny_30_ipas-path-filterpath-filter1permit.*ipas-path-filterpath-filter2deny_10_ipas-path-filterpath-filter2permit.*###interface#interface#bgprouter-id#undoimport-routedirect#BGPundoimport-routedirect#BGPMED6-6-4配置BGPMED在RouterA和RouterBRouterA和RouterC之間配置EBGPRouterB和 #BGPRouterA[RouterA]#BGPRouterA[RouterA]bgp[RouterA-bgp]router-id[RouterA-bgp]peer200.1.1.1as-number[RouterA-bgp]peer200.1.2.1as-number[RouterA-bgp]#RouterB[RouterB]bgp[RouterB-bgp]router-id[RouterB-bgp]peer200.1.1.2as-number[RouterB-bgp]peer9.1.1.2as-number[RouterB-bgp-af-ipv4]network9.1.1.0[RouterB-bgp]#RouterC[RouterC]bgp[RouterC-bgp]router-id[RouterC-bgp]peer200.1.2.2as-number[RouterC-bgp]peer9.1.1.1as-number[RouterC-bgp-af-ipv4]network9.1.1.0[RouterC-bgp]#RouterA[RouterA]displaybgprouting-table9.1.1.0BGPlocalrouterID:LocalASnumber:2available,1best,1BGProutingtableentryinformationofFrom:200.1.1.1RouteDuration:Originalnexthop:200.1.1.1Qosinformation:AS-path65009,originigp,MED0,pref-val0,valid,external,best,select,preAdvertisedtosuch2peers:Advertisedtosuch2peers:BGProutingtableentryinformationofFrom:200.1.2.1RouteDuration:Originalnexthop:200.1.2.1Qosinformation:AS-path65009,originigp,MED0,pref-val0,valid,external,pre255,notpreferredforrouterIDNotadvertisedtoanypeeryet [RouterB]route-policypolicy10permitnode[RouterB-route-policy]applycost[RouterB]bgp[RouterB-bgp]peer200.1.1.2route-policypolicy10#RouterA[RouterA]displaybgprouting-table9.1.1.0BGPlocalrouterID:LocalASnumber:2available,1best,1BGProutingtableentryinformationofFrom:200.1.2.1RouteDuration:Originalnexthop:200.1.2.1Qosinformation:AS-path65009,originigp,MED0,pref-val0,valid,external,best,select,pre255Advertisedtosuch2peers:BGProutingtableentryinformationofFrom:BGProutingtableentryinformationofFrom:200.1.1.1RouteDuration:Originalnexthop:200.1.1.1Qosinformation:AS-path65009,originigp,MED100,pref-val0,valid,external,pre255,notpreferredforMEDNotadvertisedtoanypeeryet#interface#interface#bgprouter-idpeer200.1.1.1as-numberipv4-familyunicastpeer200.1.1.1peer200.1.2.1##sysname#interfaceinterface#interface#bgprouter-idpeer9.1.1.2as-numberipv4-familyunicastnetwork9.1.1.0peer9.1.1.2peer200.1.1.2peer200.1.1.2route-policypolicy10#route-policypolicy10permitnode10applycost100##interface#interface#bgprouter-idpeer9.1.1.1as-numberundonetwork9.1.1.0peer9.1.1.1peerundonetwork9.1.1.0peer9.1.1.1peer200.1.2.2#BGP6-6-5配置BGP 配置BGP連接[RouterA]bgp[RouterA-bgp]router-id[RouterA-bgp]peer200.1.1.2as-number[RouterA-bgp]peer200.1.2.2as-number[RouterA-bgp]#RouterB[RouterB]bgp[RouterB-bgp]router-id[RouterB-bgp]peer200.1.1.1as-number[RouterB-bgp]peer200.1.3.1as-number[RouterB-bgp]#RouterC[RouterC]bgp[RouterC-bgp]router-id[RouterC-bgp]peer200.1.2.1as-number[RouterC-bgp]peer200.1.4.1as-number[RouterC-bgp]#RouterD[RouterD]bgp[RouterD-bgp]router-id[RouterD-bgp]peer200.1.3.2as-number[RouterD-bgp]peer200.1.4.2as-number[RouterD-bgp]ipv4-family[RouterD-bgp-af-ipv4]network8.1.1.0[RouterD-bgp]#RouterA[RouterA]displaybgprouting-table8.1.1.0BGPlocalrouterID:LocalASnumber:Paths:2available,Paths:2available,1best,1BGProutingtableentryinfo