路由交換基礎-OSPF協議與路由重分發(fā)

OSPF的原理與配置方法目錄鏈路狀態(tài)協議的特點單域OSPF的工作過程單域OSPF的基本配置OSPF驗證的配置方法OSPF配置的核查與排錯鏈路狀態(tài)協議的特點鏈路狀態(tài)協議的工作過程1–泛洪(Flooding)鏈路狀態(tài)信息2–構建拓撲庫3–執(zhí)行SPF算法4–構建SPF樹5–計算路由表鏈路狀態(tài)協議的特點收斂迅速:一旦發(fā)生變化受影響的源端立即發(fā)送更新信息強有力的防止環(huán)路措施：路由器了解整體的拓撲信息鏈路狀態(tài)數據包是有序且?guī)Т_認機制的SPF算法保證無環(huán)路鏈路狀態(tài)協議支持VLSM和CIDR對路由器的資源(CPU和內存)要求較高需要對網絡進行嚴格的規(guī)劃和(層次化)設計初始化過程中會產生過量的泛洪信息單域OSPF的工作過程OSPF術語InterfacesLink:對應路由器的接口Linkstate:描述路由器的接口與它鄰居工作狀態(tài)的信息：

接口的IP地址和掩碼，接口連接的網絡類型

鏈路的度量(cost)OSPF屬于鏈路狀態(tài)路由協議全部鏈路狀態(tài)信息組成一個鏈路狀態(tài)庫(LSDB)。NeighborsInterfaces構建鄰居關系有嚴格的規(guī)則!

OSPF術語NeighborsInterfacesCost=10Cost=6Cost=48CiscoOSPFCost的計算方法:

108/接口帶寬(bps)路由的度量值是路由器的某個接口到目的網絡之間所有出方向接口Cost之和。

E1(2.048-Mbps串行鏈接)=48Ethernet=10

16-MbpsTokenRing=6

FastEthernet=1問題：GigabitEthernet及更高速率=1OSPF術語AutonomousSystem(自治系統(tǒng))NeighborsInterfacesArea1Area0Cost=10Cost=6Cost=48OSPF術語RoutingTableListsBestRoutesTopologyDatabaseListsAllRoutesNeighborshipTableListsNeighborsCost=10Cost=6NeighborsInterfacesArea1Area0Cost=48AutonomousSystem(自治系統(tǒng))OSPF術語OSPF數據包類型Hello數據包數據報頭Hello數據包Helloafadjfjorqpoeru39547439070713RouterIDHello/deadintervalsNeighborsArea-IDRouterpriorityDRIPaddressBDRIPaddressAuthenticationpasswordStubareaflag**

*標記*的內容在鄰居之間必須一致HelloADECB建立鄰居關系*RouterID–在OSPF網絡中標識路由器OSPF中選擇router-id的規(guī)則：

Highestloopbackaddress

HighestactiveIPaddressLoopback接口永遠不會被動關閉。RouterIDHello/Dead間隔路由器在每個啟用OSPF的接口上發(fā)送Hello包:在多路訪問和點到點鏈路上缺省Hello間隔為10秒在NBMA網絡中缺省Hello間隔為30秒OSPF的Hello包的目的地址通常為組播地址224.0.0.5Cisco路由器上缺省的Dead間隔為Hello間隔的4倍。注意:

相鄰的路由器的Hello和Dead間隔必須一致才能建立鄰居關系，否則Hello包被丟棄。Helloafadjfjorqpoeru39547439070713RouterIDHello/deadintervalsNeighborsArea-IDRouterpriorityDRIPaddressBDRIPaddressAuthenticationpasswordStubareaflag

*

***HelloADECB建立鄰居關系標記*的內容在鄰居之間必須一致Helloafadjfjorqpoeru39547439070713相鄰兩個接口IP地址在同一子網Hello/dead間隔相同Area-ID相同如果配置驗證要求口令和驗證類型相同HelloADECB建立鄰居關系的必要條件OSPF的工作過程172.16.5.1/24E0172.16.5.2/24E1ABDownStateHelloDownState

–OSPF已啟動并且發(fā)送了Hello包，但沒有收到對端的Hello包。172.16.5.1/24E0172.16.5.2/24E1RouterBNeighborsList172.16.5.1/24,intE1IamrouterID172.16.5.1andIseenoone.DownStateInitStateABHelloOSPF的Hello數據包的目的地址通常為

224.0.0.5，其中包含RouterID信息InitState

–收到了Hello包，但其中不包含該路由器的RouterIDOSPF的工作過程172.16.5.1/24E0IamrouterID172.16.5.2,andIsee172.16.5.1.172.16.5.2/24E1RouterBNeighborsList172.16.5.1/24,intE1IamrouterID172.16.5.1andIseenoone.DownStateInitStateABHelloOSPF的工作過程172.16.5.1/24E0IamrouterID172.16.5.2,andIsee172.16.5.1.RouterANeighborsList172.16.5.2/24,intE0172.16.5.2/24E1RouterBNeighborsList172.16.5.1/24,intE1IamrouterID172.16.5.1andIseenoone.DownStateInitStateTwo-WayStateABHelloTwo-wayState–

收到Hello包，而且包含該路由器的RouterID。OSPF的工作過程OSPF的工作過程OSPF的工作過程OSPF的工作過程拓撲庫的內容一致OSPF拓撲

(網絡類型)Point-to-PointNBMABroadcast

MultiaccessX.25

FrameRelay廣播型多路訪問網DRBDR達到Two-Way狀態(tài)后選舉DR(DesignatedRouter)和BDR(BackupDesignatedRouter)代表某個廣播域每個路由器與DR和BDR的拓撲庫保持一致

(FullState)FullState:所有路由器應保持一致的拓撲庫信息注意：每個子網一對DR/BDR。P=1P=0P=1選舉DR和BDRP=3P=2DRBDRHello接口優(yōu)先級最高的路由器被選為DR，若優(yōu)先級相同RouterID最大的當選?？梢栽诮涌谏显O置優(yōu)先級，缺省為1，設置范圍是0至255，0表示不能被選為DR或BDR。向DR/BDR發(fā)送的OSPF數據包的目的地址為224.0.0.6DR向其它路由器發(fā)送的OSPF數據包的目的地址為224.0.0.5DRotherDRotherDRother一旦DR選舉完畢，一臺擁有更高優(yōu)先級的路由器加入后不會成為新的DR。如果DR失敗，BDR會成為新的DR并選舉新的BDR。P=1P=0P=1P=3P=2DRBDRHelloDRotherDRotherDRotherP=255DRother新加入的路由器對DR/BDR選舉的影響P=1P=0P=1DR的工作過程(每個子網一個DR/BDR)P=3P=2DRBDRHelloP=2P=1DRBDR2LSULSU1x4LSULSU33LSULSU---224.0.0.6LSU---224.0.0.5P=1DRotherDRotherDRotherP=1Point-to-Point鏈接通常是采用PPP或HDLC封裝的串行接口

或幀中繼/ATM中的點到點子接口

不需要選舉DR/BDROSPF自動探測這種接口類型OSPF數據包在這種網絡類型中使用目的IP地址224.0.0.5在NBMA拓撲中選舉DR/BDROSPF將NBMA看做廣播型媒介。在全網狀拓撲中要選舉DR/BDR，但NBMA網絡并不總是全網狀的。是否選舉DR/BDR取決于NBMA的拓撲，例如設置了點到點子接口的幀中繼網絡不選舉DR/BDR。X.25

FrameRelay計算路由表

TopologyTableNetCostOutInterface10.2.2.07To010.3.3.017To010.3.3.020E0Cost=10Cost=6Cost=1ABC這是去往10.3.3.0/24子網的最優(yōu)路由。10.1.1.0/2410.2.2.0/2410.3.3.0/2410.4.4.0/24Cost=10E0To0單域OSPF的基本配置單域OSPF的基本配置命令Process-id是本地有效的，不需要與其它路由器上OSPF的進程號相同。配置路由器的RouterID[H3C]router-idrouter-id

啟動OSPF協議[H3C]ospf[process-id]配置OSPF區(qū)域[H3C-ospf-1]areaarea-id在指定網段使能ospf[H3C-ospf-1-area-0.0.0.0]networkip-addresswildcard-maskOSPF配置實例路由器A:InterfaceEthernet0/0ipaddress1.1.1.1255.255.255.0InterfaceSerial0/0ipaddress2.2.2.1255.255.255.0Ospf1area0.0.0.0

network2.2.2.00.0.0.255area0.0.0.1

network1.1.1.00.0.0.255區(qū)域2區(qū)域0區(qū)域1S0/0E0/0路由器AS0/01.1.1.1/243.3.3.1/24E0/02.2.2.2/242.2.2.1/24路由器B路由器B:InterfaceEthernet0/0ipaddress3.3.3.1255.255.255.0InterfaceSerial0/0ipaddress2.2.2.2255.255.255.0Ospf1area0.0.0.0

network2.2.2.00.0.0.255area0.0.0.2

network3.3.3.00.0.0.255配置環(huán)回地址[h3c]interfaceloopback0[H3C-loopback0]ipaddress172.16.17.5255.255.255.255如果配置新的環(huán)回接口地址時，OSPF進程已經啟動，則該環(huán)回接口地址不參與RouterID的選舉，除非重新啟動路由器或關掉OSPF進程后重啟。router-idip-address

后面可跟任意的32比特IP地址(點分十進制形式)。如果執(zhí)行該命令時，OSPF進程已經啟動，需要重新啟動路由器或執(zhí)行下列命令后新的RouterID才生效:OSPFrouter-id命令[H3C][H3C]ospf1[H3C]router-id172.16.1.1[H3C]resetospf1

processresetospfprocess-id

process

[H3C]配置OSPF接口的路由器優(yōu)先級接口的DR優(yōu)先級決定了該接口在選舉DR/BDR時所具有的資格，優(yōu)先級的設置范圍是0至255,數值越大，優(yōu)先級越高。

設置為0意味著該接口所在的子網中此路由器不能被選為DR或BDR。缺省的接口優(yōu)先級是1,設備不支持在Null接口、Loopback接口上配置DR優(yōu)先級。<H3C>system-view[H3C]interfaceinterface-typeinterface-number[H3C-Ethernet1/0]ospfdr-prioritypriority設置OSPF的計時器[H3C-Ethernet1/0]ospftimerhelloseconds[H3C-Ethernet1/0]ospftimerdeadseconds如果網絡中有多個廠商的設備，可能需要調整這些間隔值。缺省情況下：在多路訪問和點到點鏈路上缺省Hello間隔為10秒，Dead間隔40秒在NBMA網絡中缺省Hello間隔為30秒，Dead間隔120秒。注意：修改Hello間隔時，Dead間隔會自動調整為Hello間隔的4倍。禁止接口發(fā)送OSPF報文缺省情況下，允許接口發(fā)送OSPF報文。禁止接口發(fā)送OSPF報文后，它將成為被動接口（Passiveinterface），不再發(fā)送Hello報文。如果要使OSPF路由信息不被某一網絡中的路由器獲得，可使用本命令禁止在此接口上發(fā)送OSPF報文。<H3C>system-view[H3C]ospf[process-id|router-idrouter-id][H3C-ospf-1]silent-interface{all|interface-typeinterface-number}default-route-advertise[always|costcost|typetype][H3C]不帶always參數時，僅當本路由器的路由表中含有缺省路由時才會向鄰居傳播0.0.0.0的缺省路由帶always參數時，

無論本路由器的路由表中是否含有缺省路由都會向鄰居傳播0.0.0.0的缺省路由在OSPF域中傳播缺省路由在OSPF域中配置缺省路由的實例CompanyXH3CAospf20area0network10.0.0.00.255.255.255

default-route-advertisealwaysiproute-static

0.0.0.00.0.0.0s0

S0PublicNetworkOSPF驗證的配置方法配置OSPF區(qū)域驗證<OutputOmitted>interfaceEthernet0ipaddress10.64.0.2255.255.255.0

ospfauthentication-modesimplecipher1234!interfaceSerial0ipaddress10.2.1.2255.255.255.0routerospf50area0network10.2.1.20.0.0.0network10.64.0.20.0.0.0

authentication-modesimpleBroadcastNetworkPoint-to-PointNetwork

E010.64.0.110.64.0.2E0

S010.2.1.210.2.1.1S1ABC<OutputOmitted>interfaceEthernet0ipaddress10.64.0.1255.255.255.0ospfauthentication-modesimplecipher1234!routerospf1area0network10.0.0.00.255.255.255

authentication-modesimple明文口令<OutputOmitted>interfaceEthernet0ipaddress10.64.0.2255.255.255.0

ospfauthentication-modemd515cipher1234!interfaceSerial0ipaddress10.2.1.2255.255.255.0<OutputOmitted>routerospf50area0network10.2.1.20.0.0.0network10.64.0.20.0.0.0

authentication-modemd5BroadcastNetworkPoint-to-PointNetwork

E010.64.0.110.64.0.2E0

S010.2.1.210.2.1.1S1ABCinterfaceEthernet0ipaddress10.64.0.1255.255.255.0

ospfauthentication-modemd515cipher1234!<OutputOmitted>routerospf1area0network10.0.0.00.255.255.255

authentication-modemd5加密口令配置OSPF區(qū)域驗證key-id

配置范圍1至255<OutputOmitted>interfaceEthernet0ipaddress10.64.0.2255.255.255.0

ospfauthentication-modesimplecipher1234!interfaceSerial0ipaddress10.2.1.2255.255.255.0<OutputOmitted>routerospf50area0network10.2.1.20.0.0.0network10.64.0.20.0.0.0BroadcastNetworkPoint-to-PointNetwork

E010.64.0.110.64.0.2E0

S010.2.1.210.2.1.1S1ABC<OutputOmitted>interfaceEthernet0ipaddress10.64.0.1255.255.255.0

ospfauthentication-modesimplecipher1234!<OutputOmitted>routerospf1area0network10.0.0.00.255.255.255配置OSPF接口驗證(簡單模式)<OutputOmitted>interfaceEthernet0ipaddress10.64.0.2255.255.255.0

ospfauthentication-modemd515cipher1234!interfaceSerial0ipaddress10.2.1.2255.255.255.0<OutputOmitted>routerospf50area0network10.2.1.20.0.0.0network10.64.0.20.0.0.0BroadcastNetworkPoint-to-PointNetwork

E010.64.0.110.64.0.2E0

S010.2.1.210.2.1.1S1ABC<OutputOmitted>interfaceEthernet0ipaddress10.64.0.1255.255.255.0

ospfauthentication-modemd515cipher1234!<OutputOmitted>routerospf1area0network10.0.0.00.255.255.255加密口令key-id

配置范圍1至255配置OSPF接口驗證一個區(qū)域中所有的路由器的驗證類型必須一致，一個網段中所有路由器的驗證字口令也必須一致。OSPF配置的核查與排錯displayiprouting-table<Sysname>displayiprouting-tableRoutingTables:PublicDestinations:6Routes:6Destination/MaskProtoPreCostNextHopInterface2.2.2.0/24Direct002.2.2.1Eth0/12.2.2.1/32Direct00127.0.0.1InLoop0127.0.0.0/8Direct00127.0.0.1InLoop0127.0.0.1/32Direct00127.0.0.1InLoop0192.168.80.0/24Direct00192.168.80.10Eth1/1192.168.80.10/32Direct00127.0.0.1InLoop0displayospfrouting<Sysname>displayospfroutingOSPFProcess1withRouterID192.168.1.2RoutingTablesRoutingforNetworkDestinationCostTypeNextHopAdvRouterArea192.168.1.0/241562Stub192.168.1.2192.168.1.20.0.0.0172.16.0.0/161563Inter192.168.1.1192.168.1.10.0.0.0TotalNets:2IntraArea:1InterArea:1ASE:0NSSA:0displayospfinterface<Sysname>displayospfinterfaceOSPFProcess1withRouterID192.168.1.1InterfacesArea:0.0.0.0IPAddressTypeStateCostPriDRBDR192.168.1.1PTPP-2-P156210.0.0.00.0.0.0Area:0.0.0.1IPAddressTypeStateCostPriDRBDR172.16.0.1BroadcastDR11172.16.0.10.0.0.0displayospfpeer<Sysname>displayospfpeerOSPFProcess1withRouterID1.1.1.1NeighborBriefInformationArea:0.0.0.0RouterIDAddressPriDead-TimeInterfaceState1.1.1.21.1.1.2140Eth0/1/0Full/DROSPF的拓撲庫displayospflsdb<Sysname>displayospflsdbOSPFProcess1withRouterID192.168.0.1LinkStateDatabaseArea:0.0.0.0TypeLinkStateIDAdvRouterAgeLenSequenceMetricRouter192.168.0.2192.168.0.247436800000040Network192.168.0.1192.168.0.132132800000030Sum-Net192.168.1.0192.168.0.132128800000021LinkStateID:產生該routerLSA的RouterID。ADVRouter:通告該routerLSA的OSPF路由器的RouterID。Age：LSA的老化時間Len：LSA的長度Sequence：LSA序列號Metric：度量值displayospfbrief顯示OSPF的概要信息。<Sysname>displayospfbriefOSPFProcess1withRouterID192.168.1.2OSPFProtocolInformationRouterID:192.168.1.2BorderRouter:NSSARouteTag:0Multi-VPN-InstanceisnotenabledApplicationsSupported:MPLSTraffic-EngineeringSPF-schedule-interval:505000LSAgenerationinterval:505000LSAarrivalinterval:1000DefaultASEparameters:Metric:1Tag:1Type:2RoutePreference:10ASERoutePreference:150SPFComputationCount:22RFC1583CompatibleAreaCount:1NssaAreaCount:1ExChange/LoadingNeighbors:0路由重分發(fā)在不同的協議轉換過渡期間特定的應用需求一種協議不能滿足所有的要求不同的行政區(qū)劃不同的域之間采用不同的路由協議設備之間不兼容不同廠商的設備互操作問題為什么需要使用多種路由協議?不同的協議采用不同的度量類型不同的度量類型之間沒有可比性需要對不同類型的度量進行轉換(Redistribution)同一臺路由設備上運行多種路由協議時選擇最優(yōu)路由的規(guī)則：

1.

首先比較雙方的管理距離(AdministrativeDistance)2.管理距離相同再比較度量172.16RIP172.16OSPFRIP172.16.0.0OSPF172.16RIP172.16OSPF不同的路由協議之間如何銜接？SeedMetric最初的度量值(seedmetric)是根據路由的直連接口確定的。不同的協議之間做路由重分發(fā)時度量的處理方式：根據初始的度量值按照該路由協議的規(guī)則繼續(xù)計算度量新設置的度量值應比該路由域中最大的度量值大RIPOSPF協議之間重分發(fā)(轉換)的命令[H3C-rip-1]import-route?bgpBorderGatewayProtocol(BGP)directConnectedegpExteriorGatewayProtocol(EGP)eigrpEnhancedInteriorGatewayRoutingProtocol(EIGRP)igrpInteriorGatewayRoutingProtocol(IGRP)isisISOIS-ISiso-igrpIGRPforOSInetworksodrOnDemandstubRoutesospfOpenShortestPathFirst(OSPF)ripRoutingInformationProtocol(RIP)staticStaticroutes缺省的SeedMetrics協議缺省的初始度量值(SeedMetrics)RIPInfinityIGRP/EIGRPInfinityOSPF20forallexceptBGP,whichis1IS-IS0BGPBGPmetricissettoIGPmetricvalue示例：重分發(fā)之前示例：重分發(fā)之前H3C配置重分發(fā)import-routerip40type2tag33cost50import-routeospfcost3示例：配置重分發(fā)之后的路由表OSPF典型案例（一）故障現象：兩臺路由器上的以太網段無法互相ping通；兩臺路由器都無法學習到對方的OSPF路由。E0/0:111.111.111.0/24FRS1/0:100.1.0.1/16S0/0:100.1.0.2/16RouterID:197.7.1.1RouterID:197.7.1.2E0/0:222.222.222.0/24RTARTBOSPF典型案例（一）RTA上的配置：

RTB上的配置：routerid197.7.1.1sysnameRTA#interfaceEthernet0/0ipaddress111.111.111.1255.255.255.0#interfaceSerial1/0link-protocolfripaddress100.1.0.1255.255.0.0ospfnetwork-typenbmafrinterface-typeDCEfrmapip100.1.0.216#ospf1peer100.1.0.2area0.0.0.0network100.1.0.00.0.255.255network197.7.1.10.0.0.0network111.111.111.00.0.0.255routerid197.7.1.2sysnameRTB#interfaceEthernet0ipaddress222.222.222.1255.255.255.0#interfaceSerial0/0clockDTECLK1link-protocolfripaddress100.1.0.2255.255.0.0ospfnetwork-typebroadcastfrmapip100.1.0.116#ospf1peer100.1.0.1area0.0.0.0network100.1.0.00.0.255.255network197.7.1.20.0.0.0network222.222.222.00.0.0.255解決問題從查看的路由器配置和相應的接口狀態(tài)信息看來，RTA和RTB相連接口的OSPF網絡類型配置得并不一致，因此導致路由計算錯誤，無法得到OSPF路由。在RTA和RTB的相應接口把網絡類型改為一致，則可以正常學習OSPF路由。改變RTB的s0/0接口的OSPF網絡類型：

[RTB-Serial0/0]ospfnetwork-typenbmaOSPF典型案例（二）故障現象：RTB和RTC之間的虛連接總是處于down狀態(tài)RTA無法訪問RTB和RTC上的Loopback網段

S1/0:55.2.1.2/24

area1

RTCarea0area1[RTB]displayospfvlinkOSPFProcess1withRouterID2.2.2.2VirtualLinksVirtual-linkNeighbor-id->3.3.3.3,State:DownCost:0State:DownType:VirtualTransitArea:0.0.0.1Timers:Hello10,Dead40,Poll0,Retransmit5,

S1/0:55.0.1.1/2455.0.1.1/24

S1/0:

S1/1:57.1.1.1/24

S1/1:55.2.1.1/24

57.1.1.2/24S1/1:

Loopback2:133.1.1.1/24

Loopback2:56.0.1.1/24

area0

area1

RTA

RTB[RTC]displayospfvlinkOSPFProcess1withRouterID3.3.3.3VirtualLinksVirtual-linkNeighbor-id->2.2.2.2,State:DownCost:0State:DownType:VirtualTransitArea:0.0.0.1Timers:Hello10,Dead40,Poll0,Retransmit5,

OSPF典型案例（二）查看路由器上的相關配置：[RTB]displaycurrent-configuration#routerid2.2.2.2sysnameRTB#……

ospf1area0.0.0.1vlink-peer3.3.3.3#[RTC]displaycurrent-configuration#routerid3.3.3.3sysnameRTC#……ospf1area0.0.0.1vlink-peer2.2.2.2#OSPF典型案例（二）查看兩臺路由器上的鄰居列表和鄰居狀態(tài)：<RTB>displayospfpeerOSPFProcess1withRouterID2.2.2.2NeighborsArea0.0.0.0interface57.1.1.1(Serial1/1)'sneighbor(s)RouterID:55.2.1.2Address:57.1.1.2State:FullMode:NbrisMasterPriority:1DR:NoneBDR:NoneDeadtimerexpiresin35sNeighborhasbeenupfor00:00:50Area0.0.0.1interface55.0.1.2(Serial1/0)'sneighbor(s)RouterID:1.1.1.1Address:55.0.1.1State:FullMode:NbrisSlavePriority:1DR:NoneBDR:NoneDeadtimerexpiresin39sNeighborhasbeenupfor00:04:57Virtuallinkwithinterface(null)'sneighborRouterID:3.3.3.3Address:(null)State:DownMode:None