第5章-IP路由基礎

1、第5章 IP路由基礎 本章主要講述IP路由的工作過程、路由表的作用以及路由分類和路由環(huán)路的產(chǎn)生與預防技術要求掌握內(nèi)容： 路由表內(nèi)容的查看及各條目的含義； 設置靜態(tài)路由； 距離向量和鏈路狀態(tài)路由協(xié)議的工作原理與特點。 章節(jié)內(nèi)容5.1 IP路由基礎5.2 靜態(tài)路由與動態(tài)路由5.3 路由環(huán)路預防技術5.4 實驗5.5 小結5.1 IP路由什么是IP路由IP路由表什么是IP路由路由器需要知道以下信息才能進行路由:目標地址如何獲得路由信息可能的路由最好的路由如何保存與驗證路由信息192.168.0.1R1R2R3R4網(wǎng)絡協(xié)議目標網(wǎng)絡ConnectedLearned10.120.2.0172.16.1.0

2、出口E0S0路由器必須學習沒有直接相連的網(wǎng)絡的信息R1什么是IP路由R2R3R4IP路由表ABCE0S0S0E0E0E1Routing TableRouting Table10. 0 2.010. 0. 3.010. 0. 4. 010. 0. 1. 00011S0S1E0S0Routing Table10. 0 3.0E0010. 0 4.0E1010. 0 2.0E0 E0 12E0S0S0120010. 0. 4. 0S0IP路由表的內(nèi)容RouterB#show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M

3、- 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, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static r

4、oute, o - ODR, P - periodic downloaded static route T - traffic engineered routeGateway of last resort is not set 10.0.0.0/24 is subnetted, 4 subnetsC 10.0.2.0 is directly connected, Serial0C 10.0.3.0 is directly connected, Ethernet0R 10.0.1.0 120/1 via 10.0.2.1, Serial0R 10.0.4.0 120/1 via 10.0.3.2

5、, Ethernet0主機路由表內(nèi)容C:route printIPv4 Route Table=Interface List0 x1 . MS TCP Loopback interface0 x10003 .00 0a eb a2 02 88 . TP-LINK 11G Wireless Adapter0 x10004 .00 e0 18 55 55 7d . HP NetServer 10/100TX PCI LAN Adapter=Active Routes:Network Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0

6、.0 100.100.109.254 100.100.109.252 30 100.100.109.0 255.255.255.0 100.100.109.252 100.100.109.252 30 100.100.109.252 255.255.255.255 127.0.0.1 127.0.0.1 30 100.255.255.255 255.255.255.255 100.100.109.252 100.100.109.252 30 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1 224.0.0.0 240.0.0.0 100.100.109.252

7、 100.100.109.252 30 255.255.255.255 255.255.255.255 100.100.109.252 100.100.109.252 1=5.2 靜態(tài)路由與動態(tài)路由靜態(tài)路由配置靜態(tài)路由（含默認路由）動態(tài)路由基礎內(nèi)部網(wǎng)關協(xié)議與外部網(wǎng)關協(xié)議管理距離路由選擇的分類靜態(tài)與動態(tài)路由靜態(tài)路由管理管理員手工輸入到路由表中動態(tài)路由使用路由協(xié)議根據(jù)網(wǎng)絡的拓撲和流量變化動態(tài)學習獲得SO靜態(tài)路由BNetworkAB承接網(wǎng)絡（Stub Network）配置靜態(tài)路由定義一個到IP目標網(wǎng)絡或子網(wǎng)的路徑Router(config)#ip route network mask address

8、 | interfacedistance permanent Stub NetworkSO靜態(tài)路由舉例BNetworkABStub Network默認路由SOBNetworkAB動態(tài)路由基礎-路由協(xié)議路由協(xié)議用來在路由器之間選擇路徑和保存路由表。網(wǎng)絡協(xié)議目標網(wǎng)絡ConnectedRIPIGRP出口E0S0S1路由協(xié)議: RIP, IGRPE0S0路由協(xié)議量化參數(shù) 結點數(shù)（hop count）帶寬（bandwidth）負載（load）延遲（delay）可靠性（reliability）代價（cost）最大傳輸單元MTU（maximum transmission unit） 量化參數(shù)（ Metric

9、s）應用56T156T1Ticks, hop countBAHop countIPXRIPIGRPBandwidthDelayLoadReliabilityMTU查看量化參數(shù)RouterB#show int e0Ethernet0 is up, line protocol is up Hardware is Lance, address is 0060.5cf3.e6b6 (bia 0060.5cf3.e6b6) Description: this port is linked to mainoffice. MTU 1500 bytes, BW 10000 Kbit, DLY 1000 use

10、c, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) ARP type: ARPA, ARP Timeout 04:00:00動態(tài)路由協(xié)議的配置定義一個IP路上協(xié)議Router(config)#router protocol keyword 指定運行路由協(xié)議的網(wǎng)絡Router(config-router)#network network-numberAutonomous System 100Autonomous System 2

11、00IGPs: RIP, IGRPEGPs: BGP自治系統(tǒng)：內(nèi)部與外部路由協(xié)議自治系統(tǒng)指一個具有統(tǒng)一管理機構、統(tǒng)一路由策略的網(wǎng)絡 IGPs 操作在自治系統(tǒng)內(nèi)部EGPs 連接不同的自治系統(tǒng)管理距離-路由協(xié)議的路由可信度 IGRPAdministrative Distance=100Router DRouter BRouter ARouter CRIPAdministrative Distance=120E我需要將一個包發(fā)送到網(wǎng)絡E，通過路由器B與C都可以到達，那么，哪一個路徑最好呢？常用協(xié)議的管理距離路由源默認值直接相連的端口0靜態(tài)路由1EIGRP90IGRP100OSPF110RIP120外

12、部EIGRP170未知/不可信的 255（不可用）路由協(xié)議的分類Distance VectorHybrid RoutingLink StateCBADCDBA距離向量協(xié)議周期性地將路由表復制鄰居路由器，累計計算距離向量CDBACBADRoutingTableRoutingTableRoutingTableRoutingTableDistanceHow farVectorIn which directionABCE0S0S0S1S0E0Routing Table 00S0S1Routing TableS00E00Routing Table E0S0 00路由表的形成過程-初使狀態(tài) ABCE0S0

13、S0S1S0E0Routing TableRouting Table0011S0S1S1S0Routing TableS00E00S0 1E0S0S0100路由表的形成過程-首次交換后 路由表的形成過程-收斂狀態(tài) ABCE0S0S0S1S0E0Routing TableRouting Table0011S0S1S1S0Routing TableS00E00S0S012E0S0S0S01200鏈路狀態(tài)路由協(xié)議初使泛洪后，基于事件觸發(fā)更新的機制傳遞變化信息Link-State PacketsSPFAlgorithmTopologicalDatabaseShortest Path First Tre

14、eRoutingTableCADB混合路由協(xié)議兼有距離向量和鏈路狀態(tài)路由協(xié)議的特點基于距離向量選擇路徑基于變化的更新機制混合路由協(xié)議5.3 路由環(huán)路預防技術路由環(huán)路的產(chǎn)生設置最大度量值反向抑制（Split Horizon）技術保持計時技術觸發(fā)更新路由環(huán)路的產(chǎn)生（一）會聚狀態(tài)ABCE0S0S0S1S0E0Routing TableS0E0S0S01200Routing TableE0S0S0S01200Routing TableS0S1S1S01100路由環(huán)路的產(chǎn)生（二）慢速匯聚產(chǎn)生了路上不一致ABCE0S0S0S1S0E0XRouting TableS0E0S0S0120DownRouting

15、 TableE0S0S0S01200Routing TableS0S1S1S01100路由器C認為到達網(wǎng)絡通過路由器路由環(huán)路的產(chǎn)生（三）ABCE0S0S0S1S0E0XRouting Table10.3.0.0S0S0S0S01210.1.0.010.2.0.010.4.0.002Routing Table10.1.0.0E0S0S0S01210.4.0.010.3.0.010.2.0.000Routing Table10.2.0.0S0S1S1S11110.1.0.010.4.0.010.3.0.000路由器A更新自己的路由表來反映新的變化，但實際上是錯誤的跳計數(shù)路由環(huán)路的產(chǎn)生（四）ABCE

16、0S0S0S1S0E0XRouting TableS0S0S0S01210.3.0.010.1.0.010.2.0.010.4.0.002Routing TableE0S0S0S01410.1.0.010.4.0.010.3.0.010.2.0.000Routing TableS0S1S1S03110.2.0.010.1.0.010.4.0.010.3.0.000路由環(huán)路的產(chǎn)生（五）信息包在三個路由器間來回傳遞網(wǎng)絡跳計數(shù)一直計數(shù)到無窮ABCE0S0S0S1S0E0XRouting TableS0S0S0S01204Routing TableE0S0S0S01610.1.0.010.4.0.01

17、0.3.0.010.2.0.000Routing TableS0S1S1S05110.2.0.010.1.0.010.4.0.010.3.0.000解決方法（ 一）：定義最大值定義一個最大值防止無限的循環(huán)計數(shù)ABCE0S0S0S1S0E0XRouting Table10.3.0.0S0S0S0S01210.1.0.010.2.0.010.4.0.0016Routing TableE0S0S0S011610.1.0.010.4.0.010.3.0.010.2.0.000Routing TableS0S1S1S016110.2.0.010.1.0.010.4.0.010.3.0.000解決方法（

18、二）：反向抑制（Split Horizon）技術 不反向通告任何從源端收到的路由更新信息 ABCE0S0S0S1S0E0XXXRouting Table10.3.0.0S0S0S0S01210.1.0.010.2.0.010.4.0.000Routing TableE0S0S0S01210.1.0.010.4.0.010.3.0.010.2.0.000Routing TableS0S1S1E11210.2.0.010.1.0.010.4.0.010.3.0.000解決方法（三）：保持計時技術 （ Hold-Down Timers）路由器在某個時間段內(nèi)拒絕任何可能會影響路由改變的信息 Network 10.4.0.0 is downthen back up then back downUpdate afterhold-down Timeis unreachableABCE0S0S0