hcie精英培训实验指导书-05bgp advance

BGP原理概作为最佳路由，并只把此路由发送给其对等体。BGPBGP的路由优选规则依次比较这些路由的BGP属性。路由属性是对路由的特定描述。Update报文中。如果缺少这类属性，路由信息就会出错。如Origin属性，AS-Path属性，Next-Hop属性；公认任意属性，所有BGP设备都可以识别此UpdateLocal_Pref属性；可选过渡属性，BGPBGP设备不识别BGPBGP设备不识别此类属性，则会被忽略该属性，且不会通告给其他对等体。如MED属性等。当到达同一目的地存在多条路由时，BGP依次对比下列属性来选择路由：依次优选手动聚合路由、自动聚合路由、network命令引入的路由、import-route命令AS依次优选Origin类型 plete的路由ASMED（MultiExitDiscriminator）值最低的路由；依次优选EBGP路由、IBGP路由；BGPIGP度量值最小的路由；优选Cluster_List最短的路由；RouterIDIP先级，BGP选路时将该路由按缺省的本地优先级100来处理。当到达同一目的地址存在多的条件是“BGP选择路由的策略”的1至8条规则中需要比较的属性完全相同。实验目BGPBGPBGPBGPAS-PathBGPMEDBGPNext-HopBGP实验内司两个不同分支机构路由器，R2R1R3上分别有设有不同的业务网段，其中192.168.10.0/24与172.16.10.0/24为业务A所用网段，192.168.20.0/24与172.16.20.0/24B所用网段。两个不同分支机构与总部间都设有专线，使得两分支机按照拓扑搭建网络，在所有AS间使用直连接口建立EBGP在公司总部AS400中，R4R5，R5R7，R7R6，R6R4IBGP邻居关系，IGP协议使用所有业务网段，与所有设备上的Loopback0所在网段都能通过BGP路由实现互相访为了使网络资源能充分得到利用，要求业务网段A的流量通过运营商设备转发，B的网络管理员进行定期线路检查，现通过适当调整IGP的链路开销值，使得所有经过总部AS的流量都沿着R4-R5-R7-R6路径转发；BB的流量单独沿着R4-R6路径转发（要求BGP路由选路与实际转发路径一致；R7BGP实验拓实验编GGLoopbackGGLoopbackGGLoopbackGGGLoopbackGGLoopbackGGGLoopbackGGLoopback验证与AS间使用直连接口建立EBGP<R1>displaybgpBGPlocalrouterID:10.0.1.1LocalASnumber:100Totalnumberofpeers:2 Peersinestablishedstate:2 ASMsgRcvdMsgSentOutQUp/Down 400400AS400中，R4R5，R5R7，R7R6，R6与R4间使用环回接口建立IBGP邻居关系，IGP协议使用OSPF[R4]displayospfpeer[R4]displayospfpeerOSPFProcess1withRouterIDPeerStatistic[R4]displaybgpBGPlocalrouterID:10.0.4.4LocalASnumber:400Totalnumberofpeers:Peersinestablishedstate:VASMsgRcvdMsgSentOutQAreaNeighbor400000:04:1904000:03:1504000:03:470所有业务网段，与所有设备上的Loopback0BGP路由<R1>displaybgprouting-tableBGPLocalrouterID<R1>displaybgprouting-tableBGPLocalrouterIDis10.0.1.1Statuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?- TotalNumberofRoutes: PrefVal00i000200*04000010020000*00*000i00iA的流量通过运营商设备转发，B的流量通过专线转发注：AS-pathBGP在ASAs-path越短越优先，BGP可以对邻居发送或接受的路由做适当修改。0*0*00*0200<R1>displaybgprouting-tableBGPLocalrouterID<R1>displaybgprouting-tableBGPLocalrouterIDis10.0.1.1Statuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?- TotalNumberofRoutes: LocPrfPrefVal<R1>tracert-a192.168.10.1tracerouteto172.16.10.1(172.16.10.1),maxhops:30,packetlength:40,pressCTRL_Ctobreak110.0.12.290ms50ms50210.0.23.3120ms60ms50<R1>tracert-a192.168.20.1tracerouteto172.16.20.1(172.16.20.1),maxhops:30,packetlength:40,pressCTRL_Ctobreak140ms30ms50260ms80ms603100ms120ms80注：MEDBGPASAS内比ASMEDMED越小越优先，BGP可<R3>displaybgprouting-tableBGPLocalrouterID<R3>displaybgprouting-tableBGPLocalrouterIDis10.0.3.3Statuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?- TotalNumberofRoutes:<R3>tracert-a172.16.10.1tracerouteto192.168.10.1(192.168.10.1),maxhops:300200*04000400*0200length:length:40,pressCTRL_Cto110.0.23.210ms40ms40210.0.12.170ms60ms40<R3>tracert-a172.16.20.1tracerouteto192.168.20.1(192.168.20.1),maxhops:30,packetlength:40,pressCTRL_Ctobreak110.0.36.610ms50ms30210.0.46.480ms60ms80310.0.14.1110ms80ms70有经过总部AS的流量都沿着R4-R5-R7-R6路径转发注：BGP255，而OSPF10150注：OSPF在引入BGP做为外部路由时，其它OSPFASBR最近的链路，此时可以通过修改接口cost来修改路径，默认接口cost为1。[R4]displayiprouting-RouteFlags:[R4]displayiprouting-RouteFlags:R-relay,D-downloadtoRoutingTables:Destinations:Routes: ProtoPreFlags[R4]displayospfOSPFProcess1withRouterID10.0.4.4RoutingTablesRoutingfor[R4]displayospf01D11IP11Routingfor11130ms30ms30280ms70ms4037041605110OSPFProcess1withRouterIDOSPFProcess1withRouterIDArea:(MPLSTEnot 101[R6]displayospfOSPFProcess1withRouterIDRouting<R1>tracert-a192.168.20.1tracerouteto172.16.20.1(172.16.20.1),maxhops:30,packetlength:40,pressCTRL_CtobreakOSPF注：BGPIBGP的水平分割，所以IBGP邻居无法正常传递路由，这里可以使用全深入理解R4R6为例，将观察到如下现象（略[R4]displaybgprouting-BGPLocalrouterIDisStatuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?- TotalNumberofRoutes:*>i00**>i00*00*0100i00*000000[R4]displayiprouting-RouteFlags:R-relay,D-downloadtoRoutingTables:Destinations: Routes: PreFlags172.16.20.0/24255RD[R6]displaybgprouting-BGPLocalrouterIDisStatuscodes:*-valid,>-best,d-h-history,i-internal,s-suppressed,S-StaleOrigin:i-IGP,e-EGP,?- TotalNumberofRoutes:PrefVal*>0 0000*00*030000**00[R6-ospf-1]displayiprouting-RouteFlags:R-relay,D-downloadtoRoutingTables:Destinations:Routes: 192.168.20.0/24IBGPPre255Flags<R1>tracert-a192.168.20.1tracerouteto172.16.20.1(172.16.20.1),maxhops:30,packetlength:40,pressCTRL_Ctobreak110.0.14.430ms50ms60210.0.46.630ms80ms90310.0.36.3100ms70ms70实现R5与R7不参与BGP路径选择BGP邻居，则可以在较稳定的一注：BGP是基于TCP的三次握制建立邻居的路由协议，在建立过程中会由一方主动发起TCP连接，如果双方都不主动发起请求，则TCP建立失败，邻居无法建立。<R4>display<R4>displaybgpBGPlocalrouterID:10.0.4.4LocalASnumber:400Totalnumberofpeers: Peersinestablishedstate: ASMsgRcvdMsgSentOutQ 4000040606<R6>displaybgpBGPlocalrouterID:10.0.6.6LocalASnumber:400Totalnumberofpeers:3 Peersinestablishedstate:2 ASMsgRcvdMsgSentOutQ 40640000406思AS400BGP路由都有两条相同下一跳的条目，为什么？AS400R5R7IBGP当R5和R7不参与，如果R4和R6连接中断后，业务B无法再通过AS400来转发流量，而是由AS200来转发。<R1>display<R1>displaycurrent-#sysnameR1interfaceipaddress10.0.14.1255.255.255.0interfaceipaddress10.0.12.1255.255.255.0interfaceipaddress10.0.1.1255.255.255.255interfaceipaddress192.168.10.1255.255.255.0interfaceipaddress192.168.20.1255.255.255.0bgprouter-idpeer10.0.12.2as-numberpeer10.0.14.4as-number400ipv4-familyunicastundosynchronization10.0.1.1peer10.0.12.2peer10.0.14.4#<R2>displaycurrent-#sysnameR2aclnumberrule5permitsource172.16.20.0aclnumberrule5permitsource192.168.20.00.0.0.255interfaceipaddress10.0.12.2255.255.255.0interfaceipaddress10.0.23.2255.255.255.0interfaceipaddress10.0.2.2255.255.255.255bgprouter-idas-numbertimerkeepalive30holdas-numbertimerkeepalive30hold#ipv4-familyunicastundosynchronizationnetwork10.0.2.2route-policyASroute-policyMED#route-policyASpermitnode10if-matchacl2000applyas-path200200additiveroute-policyASpermitnode20route-policyMEDpermitnode10if-matchacl2001applycost200route-policyMEDpermitnode20<R3>displaycurrent-#sysnameR3interfaceipaddress10.0.23.3255.255.255.0interfaceipaddress10.0.36.3255.255.255.0interfaceipaddress10.0.3.3255.255.255.255interfaceipaddress172.16.10.1255.255.255.0interfaceipaddress172.16.20.1255.255.255.0bgprouter-idpeer10.0.23.2as-numberpeer10.0.36.6as-number#ipv4-familyunicastundosynchronization10.0.3.3172.16.10.0172.16.20.0peer10.0.23.2peer10.0.36.6#<R4>displaycurrent-#sysnameR4aclnumberrule5permitsource10.0.5.5aclnumberrule5permitsource192.168.20.00.0.0.255interfaceipaddress10.0.45.4255.255.255.0interfaceipaddress10.0.14.4255.255.255.0interfaceipaddress10.0.46.4ospfcost100interfaceipaddress10.0.4.4255.255.255.255bgprouter-idpeer10.0.5.5as-numberpeer10.0.5.5peer10.0.5.5connect-interfaceLoopBack0peer10.0.6.6as-number400peer10.0.6.6connect-interfaceLoopBack0peer10.0.14.1as-number100#ipv4-familyunicastundosynchronizationnetwork10.0.4.4import-routeospf1route-policyO2Bpeer10.0.5.5enablepeer10.0.5.5next-hop-peer10.0.6.6peer10.0.6.6route-policylocalexportpeer10.0.6.6next-hop-localpeer10.0.14.1#ospf1router-idimport-routebgproute-policyB2Oarea0.0.0.0network10.0.4.4network10.0.45.4network10.0.46.4#route-policyO2Bpermitnode10if-matchacl2000#route-policylocalpermitnode10if-matchacl2001applyip-addressnext-hop10.0.46.4route-policylocalpermitnode20route-policyB2Opermitnode10if-matchacl2001#<R5>displaycurrent-#sysnameR5interfaceipaddress10.0.57.5255.255.255.0interfaceipaddress10.0.45.5255.255.255.0interfaceipaddress10.0.5.5255.255.255.255bgprouter-idas-numberconnect-interfaceas-numberconnect-interface#ipv4-familyunicastundosynchronizationreflectorcluster-id1network10.0.5.5#ospf1router-idareanetwork10.0.5.5network10.0.45.5network10.0.57.5#<R6>displaycurrent-#sysnameR6aclnumberrule5permitsource10.0.7.7aclnumberrule5permitsource172.16.20.00.0.0.255interfaceipaddress10.0.36.6255.255.255.0interfaceipaddress10.0.67.6255.255.255.0interfaceipaddress10.0.46.6ospfcost100interfaceipaddress10.0.6.6255.255.255.255bgprouter-idpeer10.0.4.4as-numberpeer10.0.4.4connect-interfaceLoopBack0peer10.0.7.7as-number400peer10.0.7.7connect-interfaceLoopBack0peer10.0.7.7listen-onlypeer10.0.36.3as-number300ipv4-familyunicastundosynchronizationnetwork10.0.6.6import-routeospf1route-policyO2Bpeer10.0.4.4enablepeer10.0.4.4next-hop-peer10.0.4.4route-policylocalexportpeer10.0.7.7enablepeer10.0.7.7next-hop-peer10.0.36.3#ospf1router-idimport-routebg