CCNA Guide to Cisco Networking Fundamentals Fourth Edition

CCNA Guide to Cisco Networking Fundamentals Fourth Edition Chapter 6 Router Startup and Configuration

Objectives • • Describe the steps involved in starting a router Describe and use the Cisco Discovery Protocol Configure IP on the Cisco router Troubleshoot router connectivity problems CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 2

Router Startup • In general, the boot process follows these steps: – – Test hardware (POST) Load the bootstrap program Locate and load the Cisco IOS Locate and load the router configuration file CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 3

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Test Hardware (POST) • Read-only memory (ROM) in a router – Typically contains the power-on self-test (POST), the bootstrap program, and often a version of the operating system • POST is a diagnostic test that determines if the hardware is operating correctly • During the POST, the bootstrap program, also called the ROM Monitor, checks basic operations of the attached hardware – The ROM Monitor checks the configuration register for instructions regarding how to load the Cisco IOS CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 5

Router Configuration Files • startup-config – The router configuration file that loads during the boot process – Sometimes referred to as the backup configuration • Because it is the saved version of the configuration file • To revert to the settings in your startup-config – Reboot the system by powering the router off and back on again or – Issue the reload command at the privileged EXEC mode prompt CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 6

Router Configuration Files (continued) • Note that when you copy over the startup configuration in NVRAM, that file is replaced • When you copy to the running configuration in RAM, the configuration files are blended • To view the contents of the startup-config – Type show startu-pconfig or just show start at the enable prompt • To see your working or running configuration – Type show running-config or just show run at the enable prompt CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 7

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Methods for Making Changes • You can usually implement and test changes without saving them to the startup configuration • Basic steps to implement changes: – – Make changes as desired to the configuration Examine those changes Determine if the changes meet the desired result Remove the changes if they do not meet the desired result, or simply reboot the router – Copy the changes from the running configuration to the startup configuration when they do meet the desired result CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 9

IP on the Router • To manually configure IP on an interface – You must first change to interface configuration mode – Then, you can use the ip address command to configure an IP address for the specific interface • In the event you are configuring a serial interface as a DCE (data communication equipment) – You will also need to add the clockrate [bandwidth in bits per second] command CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 10

IP Connectivity CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 11

Telnet • Telnet – Utility that connects at the highest layer of the OSI model and provides remote access to other devices • Cisco routers allow telnet connections via their virtual terminal ports • If you can establish telnet connectivity to a router – It is available on the network and you have connectivity at all layers CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 12

IP Host Names • Sometimes, you cannot gain connectivity because the host name that you are trying to connect with is entered in a table incorrectly • To determine the address to name mapping on your router, type: router#show hosts • To add an entry to your hosts file for name resolution – Go to global configuration mode and type: router(config)#ip host router 15 192. 168. 5. 1 CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 13

IP Host Names (continued) • To remove that entry, type: router(config)#no ip host router 15 192. 168. 5. 1 • To allow a name server to handle the IP address to name resolution, type: router(config)#ip name-server 172. 33. 44. 1 CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 14

Ping and Trace • Ping and Trace verify connectivity at the Internetwork layer of the TCP/IP model • Ping can return the following replies: !. U C I ? & Successful receipt of the ICMP echo Request timed out Destination was unreachable Congestion experienced Ping interrupted Packet type unknown Packet TTL exceeded CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 15

Ping and Trace (continued) • Using the ping command alone – Referred to as extended mode ping – Allows you to enter your ping command step by step • Trace sends multiple ICMP packets with progressively higher time-to-live counters (TTL) – Until the packet reaches the destination CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 16

Ping and Trace (continued) • The following responses can be returned by a trace: !H P N U * Indicates that a router received, but did not forward, the ICMP echo request Protocol unreachable Network unreachable Port unreachable Request timed out CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 17

IP Route • If you cannot get connectivity using Ping or Trace, you should check your routing table • Issue the show ip route command from the enable mode prompt – To display the routing table • Typically, routing tables are dynamically created when routing protocols are configured on the router – If you want, you can use the ip route command from the global configuration mode • To statically enter routes in the routing table CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 18

Checking the Interface • show interfaces command – Check the configuration of a specific interface from the enable mode prompt – Example: router#show int s 0/0 • Replies – Serial 0/0 is up, line protocol is up – Serial 0/0 is up, line protocol is down – Serial 0/0 is up, line protocol is administratively down – Serial 0/0 is down, line protocol is down CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 19

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Checking the Interface (continued) • Clear counters – The router keeps detailed statistics regarding data passing across its interfaces – To clear the counters for interface f 0/0, type: router#clear interface f 0/0 • debug command – One of the most powerful tools you can use to obtain information from your router – Tool is only available from privileged EXEC mode – Debug has numerous subcommands CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 21

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CDP • Cisco Discovery Protocol (CDP) – Cisco proprietary Data Link layer protocol • Shares configuration information between Cisco devices that are connected directly to each other • All Cisco devices can use CDP to: – Discover each other – Learn about the configurations of other devices • Using CDP can help you quickly determine the network topology • CDP was designed to be a low-overhead protocol CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 23

CDP (continued) CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 24

Cisco IOS • Cisco IOS is usually loaded from flash memory – If the router cannot find the IOS in flash memory, it will look for a copy on a TFTP server – If it cannot find one there, it will boot a minimal version of the IOS from ROM • If you want to see information about your router’s flash memory: – Type show flash from the enable mode prompt CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 25

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Cisco IOS (continued) CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 27

Configuration Register • Every Cisco router has a 16 -bit configuration register, which is stored in NVRAM • This register allows you to control several boot functions: – – – Forcing the system into the bootstrap program Enabling or disabling the console Break function Setting the console terminal baud rate Loading the IOS from ROM Loading the IOS from a TFTP server • Examine the configuration register by typing show version CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 28

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Configuration Register (continued) CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 30

ROM Monitor Mode • ROM Monitor mode – The bootstrap program that is built into the firmware of the router – Used to initialize the hardware and load the IOS – ROM Monitor can be used to perform other tasks such as diagnostics and recovering passwords • Configure your system to enter ROM Monitor mode – Enter the following command at the global configuration prompt: router(config)#config-register 0 x 2100 CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 31

ROM Monitor Mode (continued) • Configure your system to boot a smaller IOS image from ROM and enter Rx. Boot mode – Enter the following command at the global configuration prompt: router(config)#config-register 0 x 2101 CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 32

Rx. Boot Mode • Rx. Boot mode – A limited version of the IOS • Entering Rx. Boot mode is often done intentionally – When you want to access a TFTP server to download a new IOS • If your router enters Rx. Boot mode without your intervention – Indicates that the router could not find a good IOS image • Prompt: router(boot) CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 33

Boot System Commands • As long as the configuration register is configured with a 2 as the final hexadecimal digit – The ROM Monitor will look for boot system commands in NVRAM during the bootup process • Enable your system to boot an IOS file from the TFTP server – Issue the following command from global configuration mode: router(config)#boot system tftp somefile. bin CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 34

Backing Up and Restoring the IOS • copy flash tftp – The command for backing up your IOS to a TFTP server • You will be asked for the source filename, the IP address of the TFTP server, and the destination filename • Type erase flash at the privileged EXEC mode prompt – To erase the IOS CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 35

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Upgrading the IOS • Before you load a new IOS file to your router – Use the show flash command to ensure there is enough free memory to hold it • The system will tell you how much memory is used and how much is free • If there is not enough memory to hold both the current IOS image and the upgrade – You will have to erase the existing flash memory as previously mentioned CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 37

Router Password Recovery • Password recovery – Process that allows you to get into the router without the necessary passwords – You must be physically connected to the router using the console cable • Steps to perform password recovery on the Cisco 2600 series: – Connect to the router from a PC using the console port and the Hyper. Terminal program – Enter the show version command record the value of the configuration register CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 38

Router Password Recovery (continued) • Steps to perform password recovery on the Cisco 2600 series: (continued) – Turn the router off and on using the power switch – Press Ctrl+Break several times within the first 60 seconds of bootup – At the rommon 1> prompt, type confreg 0 x 2142 and press Enter – Enter the reset command at the rommon 2> prompt – Enter no if asked to enter the system configuration dialog – Enter enable to get to privileged mode CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 39

Router Password Recovery (continued) • Steps to perform password recovery on the Cisco 2600 series: (continued) – Enter the copy start run command to load the saved configuration file from NVRAM into RAM – Enter the show run command to view the configuration – To change the enable secret command, enter the following commands: Router#config t Router(config)#enable secret [secret password] CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 40

Router Password Recovery (continued) • Steps to perform password recovery on the Cisco 2600 series: (continued) – Enter config-register 0 x 2102 at the global configuration mode prompt to make sure the router reboots in the default manner – Enter the copy run start command to save your changes CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 41

Security Device Manager • Security Device Manager (SDM) – A Web-based tool primarily used for implementing and testing security configurations – Commonly used to configure routing protocols, WAN services, wireless routing, firewalls, virtual private networks (VPNs), and quality of service (Qo. S) • SDM is typically not used to configure basic functionality on a Cisco router – In fact, SDM cannot do all things CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 42

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Summary • When a router boots, it follows a set routine • Although a router’s boot process can vary, the typical boot process follows a standard sequence • 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 • If the IOS cannot be found in flash memory or on the TFTP server, then a limited version will boot from ROM CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 44

Summary (continued) • 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 • The Cisco Discovery Protocol (CDP) shares information between Cisco devices about other local Cisco devices • CDP uses broadcasts to update neighbors every 60 seconds by default • Devices share information about their interface configurations and connections to other devices CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 45

Summary (continued) • You can verify router connectivity to other systems by using telnet to determine if there is Application layer connectivity • If you cannot get connectivity at the Application layer, try Trace and Ping • One of the most important troubleshooting commands is the show interfaces command • Cisco’s Security Device Manager (SDM) is a Webbased tool designed to help you configure Cisco routers CCNA Guide to Cisco Networking Fundamentals, Fourth Edition 46