Cisco Networking Academy Program CCNA 1 and 2 Companion Guide, Revised part 84 is the Cisco approved textbook to use alongside version of the Cisco Networking Academy Program CCNA 1 and CCNA 2 web-based courses. The topics covered provide you with the necessary knowledge to begin your preparation for the CCNA certification exam (640-801, or 640-821 and 640-811) and to enter the field of network administration. | Page 799 Tuesday May 27 2003 2 19 PM Troubleshooting Router Issues Using the show interface and show interfaces Commands 799 Example 18-3 show interface serial Command Cougars show interface serial 0 Serial0 is up line protocol is up Hardware is HD64570 MTU 1500 bytes BW 1544 Kbit DLY 20000 usec reliability 255 255 txload 1 255 rxload 1 255 Encapsulation HDLC loopback not set Keepalive set 10 sec Last input never output never output hang never Last clearing of show interface counters 00 02 57 Input queue 0 75 0 0 size max drops flushes Total output drops 0 Queueing strategy weighted fair Output queue 0 1000 64 0 size max total threshold drops Conversations 0 0 256 active max active max total Reserved Conversations 0 0 allocated max allocated Available Bandwidth 1158 kilobits sec 5 minute input rate 0 bits sec 0 packets sec 5 minute output rate 0 bits sec 0 packets sec 0 packets input 0 bytes 0 no buffer Received 0 broadcasts 0 runts 0 giants 0 throttles 0 input errors 0 CRC 0 frame 0 overrun 0 ignored 0 abort 0 packets output 0 bytes 0 underruns 0 output errors 0 collisions 8 interface resets 0 output buffer failures 0 output buffers swapped out 0 carrier transitions DCD up DSR up DTR up RTS up CTS up The first parameter Serial0 is up refers to the hardware layer and essentially reflects whether the interface is receiving the carrier detect signal from the other end DCE . If the line is down a problem with the cabling might exist in a back-to-back connection with one end being administratively down. If the interface is administratively down it has been disabled manually in the configuration. The show interfaces serial command also provides information to help diagnose other Layer 1 issues that are not as easy to determine. Page 800 Tuesday May 27 2003 2 19 PM 800 Chapter 18 Basic Router Troubleshooting The following problems can be caused by an increasing number of carrier transitions counts on a serial link Line interruptions from the service
