公司一个楼层交换机cisco2960的F0/21端口自己down了，一片怨声载道，人生鼎沸，妈了个B的。通过命令：shintf0/21看到如下结果：cisco12#shintf0/21FastEthernet0/21isdown,lineprotocolisdown(err-disabled)HardwareisFastEthernet,addressis0024.1351.2e95(bia0024.1351.2e95)MTU1500bytes,BW100000Kbit,DLY100usec,reliability255/255,txload1/255,rxload1/255EncapsulationARPA,loopbacknotsetKeepaliveset(10sec)Auto-duplex,Auto-speed,mediatypeis10/100BaseTXinputflow-controlisoff,outputflow-controlisunsupportedARPtype:ARPA,ARPTimeout04:00:00Lastinput19:29:25,output19:29:20,outputhangneverLastclearingof"showinterface"countersneverInputqueue:0/75/0/0(size/max/drops/flushes);Totaloutputdrops:0Queueingstrategy:fifoOutputqueue:0/40(size/max)5minuteinputrate0bits/sec,0packets/sec5minuteoutputrate0bits/sec,0packets/sec130997686packetsinput,111565127662bytes,0nobufferReceived3733082broadcasts(0multicasts)0runts,0giants,0throttles38inputerrors,0CRC,0frame,0overrun,0ignored0watchdog,3191174multicast,0pauseinput0inputpacketswithdribbleconditiondetected121355446packetsoutput,78684231708bytes,0underruns0outputerrors,0collisions,1interfaceresets0babbles,0latecollision,0deferred0lostcarrier,0nocarrier,0PAUSEoutput0outputbufferfailures,0outputbuffersswappedout通过红色部分了解端口处于故障状态，然后通过命令shlogging看看日志，结果如下：cisco12#shloggingSysloglogging:enabled(0messagesdropped,1messagesrate-limited,0flushes,0overruns,xmldisabled,filteringdisabled)Consolelogging:leveldebugging,219messageslogged,xmldisabled,filteringdisabledMonitorlogging:leveldebugging,0messageslogged,xmldisabled,filteringdisabledBufferlogging:leveldebugging,219messageslogged,xmldisabled,filteringdisabledExceptionLogging:size(4096bytes)Countandtamploggingmessages:disabledFilelogging:disabled---本文来源于网络，仅供参考，勿照抄，如有侵权请联系删除---Traplogging:levelinformational,222messagelinesloggedLogBuffer(4096bytes):hernet0/5,changedstatetodown7w5d:%LINK-3-UPDOWN:InterfaceFastEthernet0/5,changedstatetoup7w5d:%LINEPROTO-5-UPDOWN:LineprotocolonInterfaceFastEthernet0/5,changedstatetoup7w5d:%LINEPROTO-5-UPDOWN:LineprotocolonInterfaceFastEthernet0/5,changedstatetodown7w5d:%LINEPROTO-5-UPDOWN:LineprotocolonInterfaceFastEthernet0/5,changedstatetoup7w5d:%LINEPROTO-5-UPDOWN:LineprotocolonInterfaceFastEthernet0/5,changedstatetodown7w5d:%LINK-3-UPDOWN:InterfaceFastEthernet0/5,changedstatetodown7w5d:%LINK-3-UPDOWN:InterfaceFastEthernet0/5,changedstatetoup7w5d:%LINEPROTO-5-UPDOWN:LineprotocolonInterfaceFastEthernet0/5,changedstatetoup7w5d:%LINEPROTO-5-UPDOWN:LineprotocolonInterfaceFastEthernet0/5,changedstatetodown7w5d:%LINK-3-UPDOWN:InterfaceFastEthernet0/5,changedstatetodown7w6d:%LINK-3-UPDOWN:InterfaceFastEthernet0/5,changedstatetoup7w6d:%LINEPROTO-5-UPDOWN:LineprotocolonInterfaceFastEthernet0/5,changedstatetoup7w6d:%LINEPROTO-5-UPDOWN:LineprotocolonInterfaceFastEthernet0/5,changedstatetodown7w6d:%LINEPROTO-5-UPDOWN:LineprotocolonInterfaceFastEthernet0/5,changedstatetoup7w6d:%LINEPROTO-5-UPDOWN:LineprotocolonInterfaceFastEthernet0/5,changedstatetodown7w6d:%LINEPROTO-5-UPDOWN:LineprotocolonInterfaceFastEthernet0/5,changedstatetoup7w6d:%LINEPROTO-5-UPDOWN:LineprotocolonInterfaceFastEthernet0/5,changedstatetodown7w6d:%LINK-3-UPDOWN:InterfaceFastEthernet0/5,changedstatetodown7w6d:%LINK-3-UPDOWN:InterfaceFastEthernet0/5,chang...