OSPF在NBMA下的五種網(wǎng)絡(luò)類型

OSPF在NBMA下的五種網(wǎng)絡(luò)類型與以太網(wǎng)一類的Broadcast網(wǎng)絡(luò)的區(qū)別：所謂NBMA(non-broadcastmultipleaccess)就是一個多路訪問鏈路，但不能發(fā)廣播。最典型的多路訪問鏈路就是常見的以太網(wǎng)，多個訪問節(jié)點都可以訪問同一個網(wǎng)段。在以太網(wǎng)上是可以發(fā)廣播的。所以叫BMA。NBMA阻隔廣播和組播，在幀中繼中，缺省類型就是NBMA。因為它是多路訪問鏈路，但是又由于有帶寬的限制不能發(fā)廣播包。在以太網(wǎng)中，如果你想給同一子網(wǎng)中的多臺主機發(fā)送廣播(組播)包，怎么發(fā)？很簡單，你發(fā)一個包就行了，所有的主機都收得到，這就是廣播網(wǎng)的特性。再來看幀中繼，我們以全互聯(lián)為例，雖然所有的主機都處在同一個子網(wǎng)之中，但是你不可能發(fā)一個包讓所有的主機都收到，因為實際上這個全互聯(lián)是由多個點對點組成的，要讓子網(wǎng)中的所有成員都收到這個廣播包，你只能通過所有VC向外發(fā)送這個廣播包，有幾條VC就需要發(fā)送幾個包。這就是NBMA網(wǎng)絡(luò)的特性。如果OSPF不知道底層網(wǎng)絡(luò)的通訊特性，它就不能正常工作。所以，運行于FR網(wǎng)絡(luò)之上的OSPF，即使你把接口的網(wǎng)絡(luò)類型改為broadcast，它也不是以太網(wǎng)的broadcast。所以才會有“OSPF在NBMA網(wǎng)絡(luò)中的五種網(wǎng)絡(luò)類型”這種說法。如果手工用單播地址指定鄰居，則OSPF在向和這些組播地址發(fā)送消息的同時，也會以單播的形式向相關(guān)主機發(fā)送路由信息，在這種情況下，我們還可以選擇關(guān)閉組播發(fā)送路由信息的功能，這樣就只有靜態(tài)配置的鄰居可以收到路由信息了，提高了安全性，也減少了對無關(guān)路由器的影響RequestForComments(RFC)，是一系列以編號排定的文件。RFC編輯者負責RFC以及RFC的整體結(jié)構(gòu)文檔，并維護RFC的索引。ospf把NBMA分為5類分別是RFC的：point-to-multipointnon-broadcastCISCO的：point-to-multipointnonbroadcastbroadcastpoint-to-point在NBMA網(wǎng)絡(luò)下5種網(wǎng)絡(luò)類型具體情況如下所示:網(wǎng)絡(luò)類型鄰居自動發(fā)現(xiàn)有無DRHello間隔傳輸方式Non_broadcast否有30s單播Broadcast是有10s組播Point-to-Point是無10s組播Point-to-Multipoint是無30s組播Point-to-Multipoint(nonbroadcast)否無30s單播如果在frame-relaymap語句中使用了broadcast關(guān)鍵字，那網(wǎng)絡(luò)就是廣播類型。你把默認的NBMA改成broadcast就可以發(fā)現(xiàn)鄰居了。如果不在幀中繼映句中使用broadcast,則廣播信息不能通過，這時候就只能手工指鄰居。幀中繼中的廣播多路訪問模式，是指在接口上打上ipospfnetworkbroadcast后欺騙ospf將hello包以廣播形式發(fā)送出去，但幀中繼是無法傳播廣播的，ospf通過DLCI中的broadcast來為每個具有DLCI的目的IP發(fā)送單播hello包。注意回復hello包也是單播形式艮L單播方式的hello包，形式上是借助端口下配置OSPF的broadcast方式廣播出去，但在幀中繼網(wǎng)絡(luò)中，最終還是借助幀中繼的broadcast方式來封裝廣播包為幀中繼的單播包并轉(zhuǎn)發(fā)。frame-relaymapipa.b.c.d110broadcast實驗基本配置:R1/24R1：interfaceSerial0/0ipaddressencapsulationframe-relayframe-relaymapip102ping通R1frame-relaymapip102frame-relaymapip103R2：interfaceSerial0/0ipaddressencapsulationframe-relayserialrestart-delay0 默認frame-relaymapip201frame-relaymapip201ping通R2frame-relaymapip201R3：interfaceSerial0/0ipaddressencapsulationframe-relayserialrestart-delay0frame-relaymapip301frame-relaymapip301frame-relaymapip301此時R1、R2、R3都能相互ping通R1：routerospf100router-idlog-adjacency-changesnetwork55area0network55area0R2：routerospf100router-idlog-adjacency-changesnetwork55area0network55area0R3：routerospf100router-idlog-adjacency-changesnetwork55area0network55area0Type1 Non_Broadcast(默認)Rl#showipospfneighborRl#|在R1上showipospfneighbor,發(fā)現(xiàn)沒有鄰居。說明在這種情況下鄰居需要手動配置R1：routerospf100neighborneighborR1(config-router)showipospfneiNeigliiziurIDPriStateDeadTimeAddressInterface2-2.2.21FULL/DROTHER00:01:54Serial0/03-3?3?31FULL/DR□0:01:56192.16S.1.3Serial0/0如果發(fā)現(xiàn)DR是,clearipospfproR2ttshoTiTipospfneiNeigliljurIDPriStateDeadTirn已AddressInterface1.1.!■11FULL/DROTHER00:01:44192.16S.!■1SerialO/n

R3#showipospfneiNeighborIDPri State 1 FULL/BDRDeadTime00:01:41R3#showipospfneiNeighborIDPri State 1 FULL/BDRDeadTime00:01:41AddressInterfaceSerial0/0發(fā)現(xiàn)鄰居已經(jīng)形成并且有DR與BDR的選舉!R3(config)Srouterospf100R3(config-router)#neiR3(config-router)#neighbor192.16S.1.1R3(config-router)#neighborR3(config-router)ZR3#show*Mar100:48:02.147:%SYS-5-CONFIG_I:ConfiguredfromconsolebyconsoleR3#showipospfneiNeighborIDPriStateDeadTimeAddressInterfaceN/A□ATTEMPT/DROTHER□0:01:29Serial0/01FULL/BDR00:01:50Serial0/0R3#*Mar100:49:45；.443:%OSPF-5-ADJCHG：Process100^Mbr0.0.□.0onSerial0/0fromATTEMPTtoDOWN,NeighborDown::DeadtimerexpiredR3#showipospfneiNeighhorIDPriStateDeadTirn已AddressInterfaceN/A0ATTEMPT/DROTHER—Serial0/01FULL/BDR□0:01:53Serial0/0在路由器R2、R3上設(shè)置優(yōu)先級為0,這個配置導致路由器R1變成dr,沒有bdr被選擇。R1(config-if)#ipospfprfconfig-if)#ipospfpriority?<0-255>PriorityR1(config-if)#ipospfpriority10P(config)#ints0/0(config-if)#ipospfpR2(config-if)#ipospfpriority0R3(config)#ints0/0R3(config-if)#ipospfpR3(config-if)#ipospfpriority□重啟R1ospfClearipospfprocessRl#shipospfneiNeigliborIDPriStateDeadTimeAddressInterface0FULL/DROTHER00:01:53Serial0/0B.3二3.30FULL/DROTHER00:01:36Serial0/0R2#shipospfneiNeigliborIDPriStateDeadTimeAddressInterface10FULL/DR□0:00:31Serial0/0R3#shipospfneibleigliborIDPriStateDeadTimeAddressInterface10FULL/DR□0:01:28Serial0/0鄰居已經(jīng)形成并且有DR無BDRRl#showipospfinterfaceSerialO/OisuprlineprotocolisupInternetAddress/24,Area0ProcessID100^RouterID,NetworkTypeNON_EROADCAST,Cost:64TransmitDelayis1sec,StateDR,Priority10DesignatedRouter(ID),InterfaceaddressNobackupdesignatedrouteronthisnetworkTinierintervalsconfigured^Hello30,Dead120^Wait12QfRetransmit5oob-resynctimeout12□Helloduein 14Index1/1ffloodqueuelength0Next0x0(0)/0x0(□)Lastfloodscanlengthis2finaxitnumis2Lastfloodscantinieis□nisec^maximuinis4msec在R1上查看接口R1#showipospfinterfaceNetworkTypeNON_BROADCAST,Cost:64Timerintervalsconfigured,Hello30,Dead120,Wait120,Retransmit5Priority=10,在R1上查看接口R1#showipospfinterfaceNetworkTypeNON_BROADCAST,Cost:64Timerintervalsconfigured,Hello30,Dead120,Wait120,Retransmit5Priority=10,默認為1在這種網(wǎng)絡(luò)類型中，hello的間隔是30s。打開debug信息，我們可以看到在這種網(wǎng)絡(luò)類型中，OSPF的數(shù)據(jù)包是單播傳送的。R1#lIpIjugipospfhelloOSPFhelloeventsdeljurgingisonRl#*Mar1UU:14:35.667：OSPF:Send.he1Iotoarea□onSerial0/0frriin1UU:14:3.5.667：OSPF:Sendhe1Into192.16S.1.3area□onSerial0/0trciiuRl#*Mar1UU:14:4U.U75:OSPF:RevhellofiruinareaU:fromSerial0/0192.16S.1.21UU:14:4U.U75:OSPF:EndOfhe11OpEuCESsingRl#*Mar1UU:14:.53.811：OSPF:Rc-vhellofruinareaU:fromSerial0/0*Nar1UU:14:.53.811:OSPF:Endofhe1lopirocpssingRl#*Mar1UU:15:0.5.667:OSPF:Sendhe1lotoareaUonSerial0/0frurri*Nar1UU:15:05.667：OSPF:Sendhe1lotoarea□onSerial0/0frrunRlttclekiuijripuspfhello1UU：15:10.027:OSPF:Revhe：llofruinareaUfroitiSerialu/0192.168.1.?*Nar1UU:15:1U.U27:OSPF:EndofhelloprricpssingType2 Broadcast首先去掉剛才手動配置的鄰居關(guān)系:R1(config)#routerospf100R1(config-router)#noneighborR1(config-router)#noneighbor將R1、R2和R3接口的網(wǎng)絡(luò)類型改成broadcastR1(config-router)#ints0/0R1(config-if)#ipospfnetworkbroadcastR2(config-router)#ints0/0R2(config-if)#ipospfnetworkbroadcastR3(config-router)#ints0/0R3(config-if)#ipospfnetworkbroadcast把各路由器的frame-relaymap命令加broadcast如：frame-relaymapip201b一會我們就看到了如下信息R3#*Mar100:15:12.175:%OSPF-5-ADJCHG:Process100,NbronSerial0/0fromLOADINGtoFULL,LoadingDone這說明了在這種網(wǎng)絡(luò)類型下是不需要手動配置鄰居關(guān)系的！有DR與BDR的選舉R2#showipospfinterfaceSerialO/0isup,lineprotocolisupInternetAddress/24,Area0ProcessID100,RouterIDfNetworkTypeEROAPCASTfCost:€4TransmitDelayis1sec,StateDROTHER,Priority0DesignatedRouter[ID}1.1.1.InterfaceaddressNobackupdesignatedrouteronthisnetworkTimerintervalsconfigured,Hello10,Dead40fWait40fRetransmit5□□b-resynctimeout40Helloduein00:00:01Index1/1ffloodqueuelength0Next0x0(0)/0x0(0)Lastfloodscanlengthis1fmaxinuuniis1Lastfloodscantineis0msecfmaxiiminiis□msecNeighborCountislfAdjacentneighborcountis1Adjacentwithneigtibor[DesignatedRouter)Suppresshellofor0neigirbor(s)ProcessID100,RouterID,NetworkTypeBROADCAST,Cost:64Timerintervalsconfigured,Hello10,Dead40,Wait40,Retransmit5Hello時間間隔為10s。*Mar1*Mar100:15:12.175:OSPF*Mar100:15:12.279:OSPF*Mar100:15:12.279:OSPF*Mar100:15:22.155:OSPF*Mar100:15:22.155:OSPF*Mar100:15:22.175:OSPFR2#debugipospfhelloSendhellotoarea0onSerial0/0fromRcvhellofromarea0fromSerial0/0EndofhelloprocessingRcvhellofromarea0fromSerial0/0EndofhelloprocessingSendhellotoarea0onSerial0/0from使用這個組播地址傳送數(shù)據(jù)包。Type3 Point-to-Point將R2,R3接口的網(wǎng)絡(luò)類型改成Point-to-PointR2(config-if)#ipospfnetpoint-to-point此時，R1還是BROADCAST沒有DR/BDR的選舉LOADINGtoFULL,LoadingDone說明這種網(wǎng)絡(luò)類型也不需要手動指定鄰居此時，執(zhí)行R1(config-if)#ipospfnetpoint-to-point網(wǎng)絡(luò)將變得不穩(wěn)定

R1(config-if}#*Mar100:39:03.199:%OSPF-5-ADJCHG:Process100fAdjacencyforcedtoreset*Mar100:39:03,403:%OSPF-5-ADJCHG:Proc已mm100fn:Adjacencyforcedtoresat*Mar100:39:03,495:%OSPF-5-ADJCHG:Process100rwn:Adjacencyforcedtoreset*Mar100:39:03.603:%R1(config-if}#*Mar100:39:03.199:%OSPF-5-ADJCHG:Process100fAdjacencyforcedtoreset*Mar100:39:03,403:%OSPF-5-ADJCHG:Proc已mm100fn:Adjacencyforcedtoresat*Mar100:39:03,495:%OSPF-5-ADJCHG:Process100rwn:Adjacencyforcedtoreset*Mar100:39:03.603:%OSPF-4-NONEIGHBOR:ReceivedR1(config-if}#*Mar100:39:04.227:%OSPF-5-ADJCHG:Proc已mm100fR1(config-if}#*Mar100:39:08.103:%OSPF-5-ADJCHG:Process100fAdjacencyforcedtoreset*Mar100:39:09.023:%OSPF-5-ADJCHG:Process100fR1(config-if}#*Mar100:39:13.199:%OSPF-5-ADJCHG:Proc已mm100fAdjacencyforcedtoreset*Mar100:39:13.295:%OSPF-4-NONEIGHBOR:ReceivedR1(config-if}#*Mar100:39:13,415:%OSPF-5-ADJCHG:Process100fwn:Adjacencyforcedtoreset*Mar100:39:13.619:%OSPF-5-ADJCHG:Proc已mm100fwn:AdjacencyforcedtoresetHl.fugfzL口-： NbronSerial0/0Nbr3■3■3-3onSerial0/0NbronSerial0/0fromFULLtoDOWN,NeighborDown:fromEXSTARTtoDOWNfNeighborDawfromEXCHANGEtoDOWN,NeighborDodatabasedescriptionfromunknownneighborNbr3■3■3-3onSerial0/0fromLOADINGtoFULL,LoadingDaneNbr3■3■3-3NbronSerial0/0fromFULLtoDOWN,NeighborDown:onSerial0/0fromLOADINGtoFTO.LrNbronSerial0/0fromFULLtoDOWNfLoadingDoneNeighborDown:databasedescriptionfromunknownneighborNbr3.3.3?3onSerial0/0fromEXCHANGEtoDOWN,NeighborDoNbronSerial0/0fromEXCHANGEtoDOWN,NeighborDaR2(config-if)#doshowipospfintSerial0/0isupFlineprotocolisupInternetAddress/24rArea0ProcessID100rRouterIDrNetworkTypePOINT_TO_POINTfCost:€4TransmitDelayis1secFStatePOINT_TO_POINTrTimerintervalsconfigured.Hello10rDead40rWait40rRetransmit5oob-r已mynutimeout40Helloduein00:00:04Indexl/lrfloodqueuelength0Next0x0￡0)/0x0(0)Lastflood,scanlengthis1fmaxinmniis1Lastfloodscantimeis0msecFmaxinmniis0msecNeigtiborCountislrAdjacentneighborcountis1AdjacentwithneighborSuppi?3mhell。En已：Lghbmc(m)Timerintervalsconfigured,Hello10,Dead40,Wait40,Retransmit5Hello時間間隔為10sR2#debugipospfhello*Aug1415:08:25.311:OSPF:Sendhellotoarea0onSerial0/0fromR2#*Aug1415:08:30.259:OSPF:Rcvhellofromarea0fromSerial0/0*Aug1415:08:30.263:OSPF:Endofhelloprocessing同樣也是使用這個組播地址傳送數(shù)據(jù)。重新規(guī)劃pointtopointR1重啟路由器去掉前面的配置。R1:interfaceSerial0/0noipaddressencapsulationframe-relayinterfaceSerial0/0.20point-to-pointipaddressframe-relayinterface-dlci102interfaceSerial0/0.30point-to-pointipaddressframe-relayinterface-dlci103routerospf100network55area0network55area0R2:interfaceSerial0/0ipaddressencapsulationframe-relayipospfnetworkpoint-to-pointframe-relaymapip201routerospf100network55area0R3:interfaceSerial0/0ipaddressencapsulationframe-relayframe-relaymapip301broadcastnoframe-relayinverse-arprouterospf100network55area0R2:frame-relaymapip201broadcastSerial0/OisuprlineprotocolisupInternetAddress/24fArea0ProcessID100fRouterIDfNetworkTypePOINT_TO_POINTfCost:64TransmitCtelayis1secrStatePOIErT_TO_POINTfTimerintervalsconfigured.Hello10fDeadWait40fRetransmit5□□b-resynctimeout40Helloduein00:00:07Index1/1ffloodqueuelength0Next0x0(0)/0x0[0}Lastfloodscanlengthislfmaxiiuuiuis1Lastfloodscantimeis0msecfmaximLiniis0msecNeigtiborCountislfAdjacentneigtiborcountis1AdjacentwithneigtiborSuppi?已mmh巳]口Ecii?口n巳ighbcii?(m)Type4 Point-to-Multipoint將接口改為Point-to-MultipointR1(config-if)#ipospfnetworkpoint-to-multipointR2(config-if)#ipospfnetworkpoint-to-multipointR3(config-if)#ipospfnetworkpoint-to-multipointLOADINGtoFULL,LoadingDone同樣也不需要手動指定鄰居沒有DR和BDR的選舉R2#shipospfintSerial0/Oisup,lineprotocolisupInternetAddress/24,Aj?ea0ProcessID100fRouterIDfNetworkTypePOINT_TO_MULTIPOINTfCost:岳啜TransmitDelayis1sec,StatePOINT_TO_MULTIPOINTfTimerintervalsconfigured.Hello30,Dead120,Wait120,Retransmit5oob-resynctimeout120Helloduein00:00:00Index1/1ffloodqueuelength0Next0x0[0)/0x0[0}Lastfloodscanlengthislfmaximiiniis1Lastfloodscantimeis0msec,nkaxinniniis0msecNeighborCountislfAdjacentneighborcountis1AdjacentwithneighborSuppresshellofor0neiglibor(s)NetworkTypePOINT_TO_MULTIPOINTHello30,Dead120,Wait120,Retransmit5Hello時間間隔為30sR2#*Har101:16:15.395:OSPF:Sendhelloto22^.0.0.5area0onSerialO/0fromR2#*Har101:16:40.587:OSPF:Revhellofromarea0fromSerialO/0*Mar101:16:40.587:OSPF:EndofhelloprocessingR2f*Mar101:16:45.395:OSPF:SendhelloCoarea0o