Troubleshooting Cisco IOS Software 579 Troubleshooting Cisco IOS Software Several things could prevent the router from booting properly: ■ Configuration file with a missing or incorrect boot system statement ■ Incorrect configuration register value ■ Corrupted Flash image ■ Hardware failure When the router boots, it looks in the configuration file for a boot system statement. This statement can force the router to boot from another image instead of the Cisco IOS Software image in Flash. To identify the boot image source, type the show version command and look for the line that identifies the image boot source, as shown in Example 11-18. An incorrect configuration register setting prevents the Cisco IOS Software from loading from Flash memory. The value in the configuration register tells the router where to get the Cisco IOS Software image. This can be confirmed by using the show version command and looking at the last line for the configuration register, as shown in Example 11-19. The correct value varies in different hardware platforms. The Cisco IOS Software doc- umentation should include a printed copy of the show version output. If that docu- mentation is not available, there are resources on the Cisco Documentation CD or at Cisco.com to identify the correct configuration register value. Correct this by changing the configuration register in the configuration and saving this as the startup configuration. Example 11-18 Image Boot Source Cisco> show version output omitted ROM: System Bootstrap, Version 11.0(10c), SOFTWARE BOOTLDR: 3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c), RELEASE SOFTWARE (fc1) Example 11-19 Configuration Register Cisco> show version output omitted Configuration register is 0x2102 3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c) chpt_11.fm Page 579 Wednesday, May 28, 2003 10:21 AM 580 Chapter 11: Router Fundamentals If there is still a problem, the router might have a corrupted Flash image file. If this is the case, an error message should be displayed during boot. The error message might display as follows: open: read error requested 0x4 bytes, got 0x0 trouble reading device magic number boot: cannot open "flash:" boot: cannot determine first file name on device "flash:"ú If the Flash image is corrupt, a new Cisco IOS Software image should be uploaded into the router. If the problem has not been identified in this section, the router could have a hardware failure. If this is the case, you should contact the Cisco Technical Assistance Center (TAC). Although hardware failures are rare, they do occur. Table 11-4 lists and describes other helpful router status commands. You can obtain a list of all show commands by entering the show command followed by a space and a question mark. Table 11-4 Router Status Commands Command Description show version Displays the configuration of the system hardware, the software version, the names and sources of configuration files, and the boot images, and displays the reason for the last system reboot. show processes Displays information about the active processes. show protocols Displays the configured protocols. This com- mand shows the status of any configured Layer 3 (network layer) protocol. show memory Shows statistics about the router’s memory, including memory-free pool statistics. show stacks Monitors the stack use of processes and interrupt routines. show buffers Provides statistics for the buffer pools on the router. show flash Shows information about the Flash memory device. 1102.book Page 580 Tuesday, May 20, 2003 2:53 PM Summary 581 Summary The keys points discussed in this chapter were the following: ■ Establishing a HyperTerminal session ■ Logging into the router ■ Using the help feature in the command-line interface ■ Using enhanced editing commands ■ Using command history ■ Troubleshooting command errors ■ The router can boot into either ROM monitor, boot ROM, or Cisco IOS mode. ■ The show version and show flash commands provide information on Cisco IOS Software and configuration register settings currently on the router. ■ Router commands are entered at the command-line interface (CLI) in either user EXEC, privileged EXEC, global configuration, or specific configuration mode. To supplement all that you’ve learned in this chapter, refer to the chapter-specific Videos, PhotoZooms, and e-Lab Activities on the CD-ROM accompanying this book. show running-config (write term on Cisco IOS Software Release 10.3 or earlier) Displays the active configuration file. show startup-config (show config on Cisco IOS Software Release 10.3 or earlier) Displays the backup configuration file. show interface Displays statistics for all interfaces configured. Table 11-4 Router Status Commands (Continued) Command Description 1102.book Page 581 Tuesday, May 20, 2003 2:53 PM 582 Chapter 11: Router Fundamentals Key Terms Cisco Internetwork Operating System (IOS) Software Software stored as an image file in Flash memory on the router that, when loaded into RAM, provides the operat- ing system that runs the router. command-line interface (CLI) An interface that enables the user to interact with the operating system by entering commands and optional arguments. daughter card Similar to an expansion board, but it accesses the motherboard components (memory and CPU) directly instead of sending data through the slower expansion bus. Flash memory A special type of EEPROM that can be erased and reprogrammed in blocks instead of 1 byte at a time. Many modern PCs have their BIOS stored on a Flash memory chip so that it can be updated easily, if necessary. Flash memory is also popular in modems because it enables the modem manufacturer to support new protocols as they become standardized. light-emitting diode (LED) Semiconductor device that emits light produced by converting electrical energy. Status lights on hardware devices are typically LEDs. nonvolatile RAM (NVRAM) RAM that retains its contents when a unit is powered off. power-on self-test (POST) Set of hardware diagnostics that runs on a hardware device when that device is powered up. Check Your Understanding Complete all the review questions to test your understanding of the topics and con- cepts in this chapter. Answers are listed in Appendix C, “Check Your Understanding Answer Key.” 1. A router initializes by doing which of the following? A. Loading the NVRAM, the setup procedure, and the operating system B. Loading the bootstrap, the operating system, and a configuration file C. Loading the bootstrap, the setup procedure, and the operating system 2. During the setup process in a router, what keys can be used to escape the sequence? A. Ctrl-A B. Ctrl-E C. Ctrl-C 1102.book Page 582 Tuesday, May 20, 2003 2:53 PM Check Your Understanding 583 3. Match the configuration setting on the right with the items on the left that are needed to establish a HyperTerminal session: A. BAUDNone B. DATA BITS1 C. PARITY8 D. STOP BITSNone E. FLOW CONTROL9600 4. Which of the following is true at initial boot-up output? A. The Cisco IOS Software version that the router uses can be seen. B. The Cisco IOS Software version that the router uses cannot be seen. 5. Which of the following is true at initial boot-up output? A. The amount of Flash memory can be seen. B. The amount of Flash memory cannot be seen. 6. Match the commands on the left with the correct descriptions on the right. Ctrl + a Moves out of configuration mode Ctrl + b Moves to the end of the command line Ctrl + e Moves back one word Ctrl + f Moves to the beginning of the command line Esc + b Moves forward one character Esc + f Moves forward one word Ctrl + a Moves back one character 7. Match the commands on the left with the correct descriptions on the right. Tab Enables advanced editing Ctrl + p Sets the command buffer size Ctrl + n Recalls the most recent command show history Shows the command buffer terminal history size # Recalls the last command terminal editing Completes the entry no Terminal editing Disables advanced editing features 1102.book Page 583 Tuesday, May 20, 2003 2:53 PM 584 Chapter 11: Router Fundamentals 8. What are the major elements of a typical router configuration? A. Passwords, interfaces, routing protocols, DNS B. Boot sequence, interfaces, TFTP server, NVRAM C. NVRAM, ROM, DRAM, interfaces D. Interfaces, routing protocols, configuration register, Flash memory 9. Which of the following correctly describes a method for specifying how a router loads the Cisco IOS Software? A. Designate fallback sources for the router to use in sequence from NVRAM. B. Configure the Cisco IOS software image for the location where it will bootstrap. C. Manually boot a default system image at a virtual terminal. D. Manually boot a default system image at the network server. 10. Which of the following is not a boot option that can be set with the configura- tion register boot field? A. Cisco IOS Software boots in ROM monitor mode. B. Cisco IOS Software automatically boots from ROM. C. Cisco IOS Software automatically boots from a TFTP server. D. NVRAM is examined for boot system commands. 11. Which of the following is information displayed by the Cisco IOS Software show version command? A. Detailed statistics about each page of the router’s memory B. The name of the system image C. The names and sizes of all files in Flash memory D. The status of configured network protocols 12. Which of the following has a limited version of router Cisco IOS Software? A. ROM B. Flash memory C. TFTP server D. Bootstrap 1102.book Page 584 Tuesday, May 20, 2003 2:53 PM Check Your Understanding 585 13. If you want to completely back out of configuration mode, which of the follow- ing must you enter? A. Exit B. no config-mode C. Ctrl + e D. Ctrl + z 14. If you are planning to configure an interface, what prompt should be on the router? A. router(config)# B. router(config-in)# C. router(config-intf)# D. router(config-if)# 15. What is the acronym used to describe a Cisco router’s text-based user interface? A. CLI B. TCP/IP C. OSPF D. OSI 16. What two modes of access to router commands exist for Cisco routers? A. User and privileged B. User and guest C. Privileged and guest D. Guest and anonymous 17. Which mode do you use to make router configuration changes on Cisco routers? A. User B. Privileged C. Administrator D. Root 1102.book Page 585 Tuesday, May 20, 2003 2:53 PM Objectives Upon completion of this chapter, you will be able to ■ Name a router ■ Set passwords ■ Examine show commands ■ Configure a serial interface ■ Configure an Ethernet interface ■ Execute changes to a router ■ Save changes to a router ■ Configure an interface description ■ Configure a message-of-the-day banner ■ Configure host tables ■ Describe backup documentation ■ Recover passwords 1102.book Page 586 Tuesday, May 20, 2003 2:53 PM Chapter 12 Router Configuration This chapter covers the router modes and configuration methods to update a router’s con- figuration file. It is important to have a firm understanding of Cisco IOS Software and know the procedures for starting a router. In addition, this chapter describes the tasks necessary for password recovery. Please be sure to look at this chapter’s e-Labs, Videos, and PhotoZooms that you will find on the CD-ROM accompanying this book. These CD elements are designed to supple- ment the material and reinforce the concepts introduced in this chapter. Command-Line Interface Command Modes To gain access to a router, a login is required. After login, there is a choice of modes. The modes interpret the commands that are typed and carry out the operations. Two EXEC modes exist: ■ User mode ■ Privilege mode (or enable mode) The following sections define the two command modes and their associated commands. User Command List A user is automatically in user EXEC mode upon first login to the router. User mode is a limited examination of the router. Table 12-1 provides the user mode commands and their descriptions. 1102.book Page 587 Tuesday, May 20, 2003 2:53 PM 588 Chapter 12: Router Configuration Table 12-1 User ModeCommands Command Description access-enable Creates a temporary access list entry atmsig Executes ATM signaling commands cd Changes current device clear Resets functions connect Opens a terminal connection dir Lists files on a given device disable Turns off privileged commands disconnect Disconnects an existing network enable Turns on privileged commands exit Exits EXEC help Gets a description of the interactive help system lat Opens a LAT connection lock Locks the terminal login Logs in as a particular user logout Exits EXEC mode mrinfo Requests neighbor and version information from a multicast router mstat Shows statistics after multiple multicast traceroutes mtrace Traces the reverse multicast path from destination to source name-connection Names an existing network connection pad Opens an X.29 PAD connection ping Sends echo messages ppp Starts IETF Point-to-Point Protocol (PPP) pwd Displays current device resume Resumes an active network connection rlogin Opens an rlogin connection N O TE At this point, the list of commands displayed is context sensitive. You see a different list when you are in user mode versus enable mode, and when in global configuration mode versus configure inter- face modes. 1102.book Page 588 Tuesday, May 20, 2003 2:53 PM . Table 12 -1 provides the user mode commands and their descriptions. 11 02. book Page 587 Tuesday, May 20 , 20 03 2: 53 PM 588 Chapter 12 : Router Configuration Table 12 -1 User ModeCommands Command Description access-enable. register is 0x 21 0 2 3000 Bootstrap Software (IGS-BOOT-R), Version 11 .0 (10 c) chpt _11 .fm Page 579 Wednesday, May 28 , 20 03 10 : 21 AM 580 Chapter 11 : Router Fundamentals If there is still a problem, the router. Software (IGS-BOOT-R), Version 11 .0 (10 c), RELEASE SOFTWARE (fc1) Example 11 -19 Configuration Register Cisco> show version output omitted Configuration register is 0x 21 0 2 3000 Bootstrap Software