网络简单排错

1、网络简单排错课程内容常用CISCO故障排除命令网络常见问题察看路由器状态的命令RAMInternetwork Operating SystemProgramsTables and BuffersDynamicConfigurationInformationNVRAMFlashBackupConfigurationFileOperating SystemsInterfacesRouter#show interfacesRouter#show memRouter#show ip routeRouter#show flashRouter#show startup-configRouter#show

2、running-configRouter#show processes CPURouter#show protocolsRouter#show versionRouter#show versionIOS (tm) 2500 Software (C2500-JS-L), Version 11.2 (6), RELEASE SOFTWARE (fc1)Copyright (c) 1986-1997 by cisco Systems, Inc.Compiled Tue 06-May-97 16:17 by kuongImage text-base: 0 x0303ED8C, data-base: 0

3、 x00001000ROM: System Bootstrap, Version 5.2(8a), RELEASE SOFTWAREROM: 2500-XBOOT Bootstrap Software, Version 10.1(1), RELEASE SOFTWARE (fc1) router uptime is 1 week, 3 days, 32 minutesSystem restarted by reloadSystem image c2500-js-l, booted via t 29-More-show version 命令Router#show startup-configUs

4、ing 1108 out of 130048 bytes!version 11.2!hostname router- More -show startup-config 命令和 show running-config 命令10.2及 以前版本使用Use write terminal命令10.2 以后版本使用show config命令Router#show running-configBuilding configuration.Current configuration:!version 11.2!- More -Router#show interfaces Serial0 is up, li

5、ne protocol is up Hardware is MK5025 Internet address is 29, subnet mask is 28 MTU 1500 bytes, BW 56 Kbit, DLY 20000 usec, rely 255/255, load 9/255 Encapsulation HDLC, loopback not set, keepalive set (10 sec) Last input 0:00:00, output 0:00:01, output hang never Last clearing of show interface count

6、ers never Output queue 0/40, 0 drops; input queue 0/75, 0 drops Five minute input rate 1000 bits/sec, 0 packets/sec Five minute output rate 2000 bits/sec, 0 packets/sec 331885 packets input, 62400237 bytes, 0 no buffer Received 230457 broadcasts, 0 runts, 0 giants 3 input errors, 3 CRC, 0 frame, 0 o

7、verrun, 0 ignored, 0 abort 403591 packets output, 66717279 bytes, 0 underruns 0 output errors, 0 collisions, 8 interface resets, 0 restarts 45 carrier transitionsshow interfaces 命令clear counters CommandRouter show int s 1Serial1 is up, line protocol is up Hardware is cxBus Serial Description: 56Kb L

8、ine San Jose - MP Internet address is 03, subnet mask is MTU 1500 bytes, BW 56 Kbit, DLY 20000 usec, rely 255/255, load 1/255 Encapsulation HDLC, loopback not set, keepalive set (10 sec) Last input 0:00:07, output 0:00:00, output hang never Last clearing of show interface counters 2w4d Output queue

9、0/40, 0 drops; input queue 0/75, 0 drops Five minute input rate 0 bits/sec, 0 packets/sec Five minute output rate 0 bits/sec, 0 packets/sec 16263 packets input, 1347238 bytes, 0 no buffer Received 13983 broadcasts, 0 runts, 0 giants 2 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 2 abort 0 inp

10、ut packets with dribble condition detected 22146 packets output, 2383680 bytes, 0 underruns 0 output errors, 0 collisions, 2 interface resets, 0 restarts 1 carrier transitionsRouter# clear countersshow interfaces CommandRouter show interfacesEthernet 0 is up, line protocol is upHardware is MCI Ether

11、net, address is 0000.0c00.750c (bia 0000.0c00.750c)Internet address is , subnet mask is MTU 1500 bytes, BW 10000 Kbit, DLY 100000 usec, rely 255/255, load 1/255Encapsulation ARPA, loopback not set, keepalive set (10 sec)ARP type: ARPA, ARP Timeout 4:00:00Last input 0:00:00, output 0:00:00, output ha

12、ng neverLast clearing of “show interface” counters 0:00:00Output queue 0/40, 0 drops; input queue 0/75, 0 dropsFive minute input rate 0 bits/sec, 0 packets/secFive minute output rate 2000 bits/sec, 4 packets/sec1127576 packets input, 447251251 bytes, 0 no bufferReceived 354125 broadcasts, 0 runts, 0

13、 giants0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort5332142 packets output, 496316039 bytes, 0 underruns0 output errors, 432 collisions, 0 interface resets, 0 restarts-More-show interfaces ethernet CommandRouter show interfaces ethernet 0Ethernet 0 is up, line protocol is upHardware

14、is MCI Ethernet, address is aa00.0400.0134 (bia 0000.0c00.4369)Internet address is , subnet mask is MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, rely 255/255, load 1/255Encapsulation ARPA, loopback not set, keepalive set (10 sec)ARP type: ARPA, PROBE, ARP Timeout 4:00:00Last input 0:00:00, output 0

15、:00:00, output hang neverLast clearing of “show interface” counters 0:56:40Output queue 0/40, 0 drops; input queue 0/75, 2 dropsFive minute input rate 6100 bits/sec, 4 packets/secFive minute output rate 1000 bits/sec, 2 packets/sec2295197 packets input, 305539992 bytes, 0 no bufferReceived 1925500 b

16、roadcasts, 0 runts, 0 giants3 input errors, 3 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort0 input packets with dribble condition detected3594664 packets output, 436549843 bytes, 0 underruns8 output errors, 1790 collisions, 10 interface resets, 0 restarts以太网帧（数据链路层）格式（总长度641518字节 = 601518 + 4bytes CRC

17、）最后四字节为数据链路层CRC校验值CRC错误而数据段正常(60-1514)则为普通CRC校验错误CRC正确而数据段1514字节,则被称为Oversize错误CRC错误且数据段1514字节被称为Jabber一个数据帧尾没有形成一个完整的Byte时被称为alignment错误当产生JAM信号,并且出现Runt/Fragment/CRC错误时候,则为collision这些错误的产生的可能原因在Sniffer Pro的专家系统里有更加详尽的解释解释Router#show protocolsGlobal values: Internet Protocol routing is enabled DECN

18、ET routing is enabled XNS routing is enabled Vines routing is enabled Appletalk routing is enabled Novell routing is enabled -More- Ethernet0 is up, line protocol is up Internet address is , subnet mask is 28 Decnet cost is 5 XNS address is 3010.aa00.0400.0284 CLNS enabled Vines metric is 32 AppleTa

19、lk address is 3012.93, zone ld-e0 Novell address is 3010.aa00.0400.0284 -More-show protocols 命令检验配置的地址ApplicationTransportInternetNetwork InterfaceHardwareTelnetICMPtracepingApplicationTransportInternetNetwork InterfaceHardwareTelnetICMPtracetelnettrace检查IP网络的连通性简化的PingRouter ping Type escape sequen

20、ce to abort.Sending 5, 100-byte ICMP Echos to , timeout is 2 seconds:.!Success rate is 80 percent, round-trip min/avg/max = 6/6/6 msRouter很多协议都支持ping扩展的 PingRouter# pingProtocol ip:Target IP address: 62Repeat count 5:Datagram size 100:Timeout in seconds 2:Extended commands n: ySource address:Type of

21、 service 0:Set DF bit in IP header? no: yesData pattern 0 xABCD:Loose, Strict, Record, Timestamp, Verbosenone:Sweep range of sizes n:Type escape sequence to abort.Sending 5, 100-byte ICMP Echos to 62, timeout is 2 seconds:!Success rate is 100 percent (5/5), round-trip min/avg/max = 24/26/28 msRouter#显示从源到目的所有经过端口的IP地址IP TraceRouter# trace Type escap