Chapter 07


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Chapter 07

  1. 1. CHAPTER SEVEN Router Startup and Configuration
  2. 2. Objectives <ul><li>Understand router setup and startup </li></ul><ul><li>Describe and use the Cisco Discovery Protocol </li></ul><ul><li>Understand configuration management commands for Cisco routers and the 1900 series switch </li></ul><ul><li>Configure IP on the Cisco router and the 1900 series switch </li></ul><ul><li>Troubleshoot router connectivity problems </li></ul>
  3. 3. Router Setup and Startup <ul><li>A router follows a specific boot process, but processes can vary </li></ul><ul><li>In general, the boot process follows these steps: </li></ul><ul><ul><li>Test hardware (POST) </li></ul></ul><ul><ul><li>Load bootstrap </li></ul></ul><ul><ul><li>Locate and load Cisco IOS </li></ul></ul><ul><ul><li>Locate and load router configuration file </li></ul></ul>
  4. 4. Router Setup and Startup Figure 7-1: The boot process
  5. 5. POST <ul><li>Power-on self test (POST) </li></ul><ul><ul><li>Diagnostic program in ROM that runs when the router is powered on </li></ul></ul><ul><li>ROM Monitor </li></ul><ul><ul><li>Bootstrap program that runs during the power-on self test and checks basic operations of hardware </li></ul></ul><ul><ul><li>ROM Monitor checks the configuration register for instructions regarding how to load the Cisco IOS </li></ul></ul>
  6. 6. POST <ul><li>Configuration register allows you to control several boot functions, including: </li></ul><ul><ul><li>Forcing the system into the bootstrap program </li></ul></ul><ul><ul><li>Enabling or disabling the console Break function </li></ul></ul><ul><ul><li>Setting the console terminal baud rate </li></ul></ul><ul><ul><li>Loading the IOS from ROM </li></ul></ul><ul><ul><li>Loading the IOS from a TFTP server </li></ul></ul>
  7. 7. POST Figure 7-2: Output from the show version command
  8. 8. POST Table 7-1: Configuration register codes
  9. 9. Monitor Mode <ul><li>You can set the router to enter ROM Monitor mode during the boot process by modifying the configuration register </li></ul><ul><li>ROM Monitor mode </li></ul><ul><ul><li>Router mode in which you can configure the router manually </li></ul></ul><ul><ul><li>You must provide each command in the correct syntax in order to configure the router </li></ul></ul>
  10. 10. Cisco IOS Figure 7-3: Output from the Cisco 2500 series router on bootup
  11. 11. Cisco IOS <ul><li>Trivial File Transfer Protocol (TFTP) server </li></ul><ul><ul><li>Computer (such as a PC, UNIX workstation, or laptop) running TFTP server services </li></ul></ul>Figure 7-4: Output from the show flash command
  12. 12. Cisco IOS <ul><li>Cisco routers support the following fallback options for loading the IOS: </li></ul><ul><ul><li>If the IOS is configured to load from a TFTP server, but that server cannot be located, the IOS is loaded from flash memory </li></ul></ul><ul><ul><li>If the IOS cannot be found in flash or on a TFTP server, a minimal version of the IOS is loaded from ROM </li></ul></ul>
  13. 13. Booting from TFTP <ul><li>You can force the router to load its IOS from a TFTP server by putting boot system commands into the configuration file </li></ul><ul><li>Global configuration mode </li></ul><ul><ul><li>Router mode that allows you to manipulate most of the router’s generic settings </li></ul></ul><ul><ul><li>Prompt for global configuration mode is router(config)# </li></ul></ul>
  14. 14. Upgrading the IOS <ul><li>Before loading a flash file to a router, use the show flash command to ensure there is enough free memory to load the new Cisco IOS software </li></ul><ul><ul><li>The system will tell you how much memory is used and how much is free </li></ul></ul><ul><ul><li>You may have to erase the existing flash memory before writing onto it due to space limitations </li></ul></ul>
  15. 15. RXBoot Mode <ul><li>Another configuration mode that you can enter when: </li></ul><ul><ul><li>The changes to your system make it impossible to boot from the flash memory </li></ul></ul><ul><ul><li>You cannot locate a valid IOS image </li></ul></ul><ul><li>The prompt from RXBoot mode is the hostname of your router followed by “boot” in parentheses </li></ul>
  16. 16. Cisco Catalyst 1900 IOS and Configuration Management <ul><li>To upgrade or restore IOS via TFTP, the command syntax is copy tftp://tftp_server_address/IOS_file/ opcode </li></ul><ul><ul><li>The opcode command tells the device to load the file into flash memory </li></ul></ul><ul><li>To backup configuration settings for a Catalyst 1900 switch, copy contents of NVRAM to a TFTP server </li></ul><ul><ul><li>The command syntax is copy nvram tftp://tftp_server_address/config_file_name </li></ul></ul>
  17. 17. Router Configuration Files Table 7-2: Important router copy commands
  18. 18. Router Configuration Files Table 7-2 (cont.): Important router copy commands
  19. 19. Methods for Making Changes <ul><li>When changes to a router’s configuration or boot process are required, these basic steps can be used: </li></ul><ul><ul><li>Make changes as desired to the running configuration </li></ul></ul><ul><ul><li>Examine those changes </li></ul></ul><ul><ul><li>Determine if the changes meet the desired result </li></ul></ul><ul><ul><li>Remove the changes if they do not meet the desired result, or simply reboot the router </li></ul></ul><ul><ul><li>Copy the changes from the running configuration to the startup configuration when they do meet the desired result </li></ul></ul>
  20. 20. CDP <ul><li>Cisco Discovery Protocol (CDP) </li></ul><ul><ul><li>Cisco proprietary Data Link layer protocol </li></ul></ul><ul><ul><li>Shares configuration information between Cisco devices connected locally to each other </li></ul></ul><ul><ul><li>Using CDP can help you quickly determine the network topology </li></ul></ul><ul><ul><li>With CDP, you can discover other devices on the same LAN segment and those connected over a serial interface </li></ul></ul>
  21. 21. CDP Figure 7-5: Show CDP neighbor command
  22. 22. CDP <ul><li>The show CDP neighbor command supports the following options: </li></ul><ul><ul><li>Ethernet </li></ul></ul><ul><ul><li>Null </li></ul></ul><ul><ul><li>Serial </li></ul></ul><ul><ul><li>Detail </li></ul></ul><ul><li>CDP was designed to be a low-overhead protocol </li></ul>
  23. 23. IP on the Router <ul><li>If the router is initially configured using the extended setup program, you will be asked if you would like to enable the IP on your router </li></ul><ul><ul><li>If yes, you are prompted to configure IP on each of interface you wish to set up </li></ul></ul><ul><ul><li>If no, you can either run setup again later, or you can configure the interfaces manually </li></ul></ul><ul><li>In the event you are configuring a serial interface as a DCE (data communication equipment) , you will also need to add the clockrate command </li></ul>
  24. 24. IP on the Switch <ul><li>An IP address is not necessary on a switch like the Catalyst 1900 </li></ul><ul><ul><li>Switches operate mainly on Layer 2 (MAC addresses) </li></ul></ul><ul><li>You may wish to configure an IP address for your switch so you can manage it over the network via Telnet or some other management software </li></ul><ul><ul><li>In order to set an IP address, you must enter Global Configuration mode by typing configure terminal (or one of its abbreviations) </li></ul></ul>
  25. 25. IP Connectivity Table 7-3: Testing connectivity by layer
  26. 26. Telnet <ul><li>Utility that connects at the highest layer of the OSI model </li></ul><ul><li>Provides remote access to other devices </li></ul><ul><li>Cisco routers allow telnet connections via their virtual terminal ports </li></ul><ul><li>If you can establish telnet connectivity to a router, you have established that it is available on the network and that you have connectivity at all layers </li></ul>
  27. 27. IP Host Names <ul><li>When telnetting to a remote router or host, the IP address of the host must follow the telnet command </li></ul><ul><li>Rather than using IP addresses, it is easier to refer to a remote host or router using a name </li></ul><ul><li>Sometimes, you cannot gain connectivity because the host name that you are trying to connect with is entered in a table incorrectly </li></ul><ul><li>Using a name server provides name resolution from one location, making a table configuration on each device unnecessary </li></ul>
  28. 28. Ping and Trace <ul><li>If you can’t get connectivity at the Application layer, try connectivity at the Internetwork layer </li></ul><ul><li>Ping and trace verify connectivity at the Internetwork layer </li></ul><ul><ul><li>Both use ICMP messages to verify the destination host is reachable, and if not, give possible reasons for the problem </li></ul></ul><ul><li>Ping sends a packet to the destination and waits for a response </li></ul><ul><ul><li>By default, the ping utility with Cisco routers is configured to send five packets to the target </li></ul></ul>
  29. 29. Ping and Trace <ul><li>Ping can return the following replies: </li></ul><ul><ul><li>! </li></ul></ul><ul><ul><li>. </li></ul></ul><ul><ul><li>U </li></ul></ul><ul><ul><li>C </li></ul></ul><ul><ul><li>I </li></ul></ul><ul><ul><li>? </li></ul></ul><ul><ul><li>& </li></ul></ul>
  30. 30. Ping and Trace <ul><li>Extended mode ping </li></ul><ul><ul><li>Options include: </li></ul></ul><ul><ul><ul><li>The destination address of the ping </li></ul></ul></ul><ul><ul><ul><li>The protocol </li></ul></ul></ul><ul><ul><ul><li>Repeat count </li></ul></ul></ul><ul><ul><ul><li>Datagram size </li></ul></ul></ul><ul><ul><li>Can only be accessed from the privileged mode prompt </li></ul></ul>
  31. 31. Ping and Trace <ul><li>If ping indicates a problem with connectivity, using trace may provide a better clue as to the source of the connectivity problem </li></ul><ul><li>Trace command is similar to ping command, except that the replies are requested at each hop along the way to the destination </li></ul><ul><li>Trace sends multiple ICMP packets with progressively higher TTL counters until the packet reaches the destination </li></ul>
  32. 32. Ping and Trace <ul><li>The following responses can be returned by a trace: </li></ul><ul><ul><li>!H </li></ul></ul><ul><ul><li>P </li></ul></ul><ul><ul><li>N </li></ul></ul><ul><ul><li>U </li></ul></ul><ul><ul><li>* </li></ul></ul>
  33. 33. IP Route <ul><li>If you cannot get connectivity using ping or trace, you should check your routing table </li></ul><ul><li>You can issue the show ip route command from the enable mode prompt </li></ul><ul><ul><li>This command shows the routing table </li></ul></ul><ul><li>Typically, routing tables are dynamically created when routing protocols are configured on the router </li></ul>
  34. 34. Checking the Interface <ul><li>On of the biggest mistakes made when troubleshooting is not checking the interfaces on the router </li></ul><ul><li>If the interfaces are down, packets cannot be delivered </li></ul><ul><li>Router interfaces go down for a variety of reasons including: </li></ul><ul><ul><li>Incorrect IP configuration </li></ul></ul><ul><ul><li>Cable problems </li></ul></ul>
  35. 35. Checking the Interface <ul><li>Keepalive frames </li></ul><ul><ul><li>Data frames sent between two hosts to ensure that the connection between those hosts remains open </li></ul></ul><ul><li>Different types of interfaces can show different types of reports </li></ul><ul><ul><li>For example, a Token Ring interface reports down when there is no electrical carrier signal present </li></ul></ul>
  36. 36. Checking the Interface Figure 7-6: Output from the show interfaces command
  37. 37. Clear Counters <ul><li>Routers keep detailed statistics regarding the data passing across its interfaces </li></ul><ul><li>Before using the show interface command, you may want to clear the existing interface information </li></ul><ul><li>You can clear these statistics ( counters ) on the interface by using the clear interface or clear counters command </li></ul>
  38. 38. Debug <ul><li>Debug command </li></ul><ul><ul><li>One of the most powerful tools you can use to obtain information from your router </li></ul></ul><ul><ul><li>Only available from privileged EXEC mode </li></ul></ul><ul><ul><li>Has numerous subcommands that allow you to troubleshoot particular protocols </li></ul></ul><ul><ul><li>Allows you to check for specific types of traffic on the wire </li></ul></ul>
  39. 39. Debug Figure 7-7: Debug all command output
  40. 40. Chapter Summary <ul><li>When the router boots, it follows a set routine </li></ul><ul><li>If the Cisco IOS is set to load from a TFTP server, but the TFTP server cannot be located, then the IOS will boot from flash memory </li></ul><ul><li>If the IOS cannot be found in flash memory or on the TFTP server, a limited version will boot from ROM </li></ul><ul><li>If the Cisco IOS is set to load a configuration file from a TFTP server, but the file or server is not available, the configuration file will be loaded from NVRAM </li></ul>
  41. 41. Chapter Summary <ul><li>CDP is proprietary to Cisco devices </li></ul><ul><li>Devices share information about their interface configurations and connections to other devices </li></ul><ul><li>IP configuration on Cisco switches is similar </li></ul><ul><li>When you configure an address for a router interface, you must be in interface configuration mode </li></ul><ul><li>When you configure an IP address for a Catalyst 1900 switch, you need only be in global configuration mode </li></ul>
  42. 42. Chapter Summary <ul><li>You can verify router connectivity to other systems by using telnet to determine if there is Application layer connectivity </li></ul><ul><li>If you cannot get connectivity at the Application layer, try trace and ping </li></ul><ul><li>On of the most important troubleshooting commands is the show interface command </li></ul>