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Sybex CCNA 640-802 Chapter 5: Managing a Cisco Internetwork

Sybex CCNA 640-802 Chapter 5: Managing a Cisco Internetwork. Chapter 5 Objectives. Cisco Router Component s Boot Sequence Configuration register Backing up and restoring the IOS Backing up and restoring the configuration Cisco Discovery Protocol Telnet Resolving hostnames

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Sybex CCNA 640-802 Chapter 5: Managing a Cisco Internetwork

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  1. Sybex CCNA 640-802 Chapter 5: Managing a Cisco Internetwork

  2. Chapter 5 Objectives • Cisco Router Components • Boot Sequence • Configuration register • Backing up and restoring the IOS • Backing up and restoring the configuration • Cisco Discovery Protocol • Telnet • Resolving hostnames • Troubleshooting tools 2

  3. Cisco Router Components • Bootstrap • Brings up the router during initialization • POST • Checks basic functionality; hardware & interfaces • ROM monitor • Manufacturing testing & troubleshooting • Mini-IOS • Loads Cisco IOS into flash memory • RAM • Holds packet buffers, routing tables, & software • Stores running-config

  4. Cisco Router Components (cont) • ROM • Starts & maintains the router • Flash Memory • Holds Cisco IOS • Not erased when the router is reloaded • NVRAM • Holds router (& switch) configurations (startup-config) • Not erased when the router is reloaded • Configuration Register • Controls how the router boots up

  5. Boot Sequence 1: Router performs a POST 2: Bootstrap looks for & loads the Cisco IOS 3:IOS software looks for a valid configuration file 4: Startup-config file (from NVRAM) is loaded • If startup-config file is not found, the router will start the setup mode

  6. ConfigurationRegisters • Register • 16-bit software written into NVRAM • Loadsfrom flash memory & looks for the startup-config file • Configuration Register Bits • 16 bits read 15-0, from left to right • default setting: 0x2102 Register 2 1 0 2 , Bit number 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Binary 0 0 1 0 0 0 0 1 0 0 0 0 0 0 1 0 • NOTE: 0x means the digits that follow are in hexadecimal • You read the numbers in the “Binary” (lower) line above as four groups of four bits each. • Each group reads across: “8 4 2 1”, so in the binary line, the groups are: • 0 0 1 0 = 2, 0 0 0 1 = 1, 0 0 0 0 = 0, and 0 0 1 0 = 2 • The entire row, therefore, reads “2102”

  7. ConfigurationRegisters (cont) Register 2 1 0 2 , Bit number 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Binary 0 0 1 0 0 0 0 1 0 0 0 0 0 0 1 0 • The characters “0x” indicates that the following digits are in hexadecimal. • Note that with reference to the config register, each hex character translates as a separate “nibble”, or a 4-bit, binary number. • This is why the hex 0x2102 translates as the “Binary” line above

  8. ConfigurationRegisters (cont) • The lowest four bits of the configuration register (bits 3, 2, 1, and 0) form the boot field. The order in which the switch/router looks for system bootstrap informationdepends on the boot field setting in the configuration register. • When the boot field is set to either0 or 1 (0-0-0-0 or 0-0-0-1), the system ignores any boot instructions in the system configuration file and the following occurs: • When the boot field is set to 1 you will boot from an IOS image stored in ROM. • When the boot field is set to 0, you must boot the operating system manually by giving a boot command to the system bootstrap program, or ROM monitor(ROMmon mode).

  9. Configuration Registers (full text)

  10. Checking the Register Value Router#shversion Cisco Internetwork Operating System Software IOS ™ C2600 Software (C2600-I-M), Version 12.0(3)T3 RELEASE SOFTWARE (fc1) [output cut] Configuration register is 0x2102

  11. Configuration Meanings

  12. Boot Field Meanings(Config Register bits 00 – 03)

  13. Changingthe Configuration Register • Why would you want to change the config register? Several reasons: • to forcethe system into the ROM monitor mode • to select a boot source & default boot filename • to enable or disable the Break function • to set the console terminal baud rate • to load operating software from ROM • to enable booting from a TFTP server

  14. Changing the Configuration Register One way to change the config register is to use the command below: Router(config)#config-register 0x0101 Router(config)#^Z Router#sh ver Configuration register is 0x2102 (will be 0x0101 at next reload) • The command displays both the current value of the config register as well as the value at the next reload.

  15. Recovering Passwords 1: Boot the router 1(a): interrupt the boot sequence by performing a break 2: Change the configuration register to turn on bit 6 (0x2142) 3: Reload the router 4: Enter the privileged mode 5: Copy the startup-config to running-config 6: Change the password 7: Reset the configuration register to the default value 8: Reload the router Note: You need physical access to the router to do this.

  16. Recovering Passwords – (Step by step) 1: Boot the router & interrupt the boot sequence by performing a break using the Ctrl+Break key combination. You may need to upgrade your version of hyper-terminal in order for this to work successfully. (I’ve never had to do this, and I’ve used some pretty old versions of HyperTerminal; grain of salt here).

  17. Recovering Passwords 2: Change the configuration register to turn on bit 6(0x2142) rommon>confreg 0x2142 You must reset or power cycle for new config to take effect 3: Reloadthe router • Type reset • The router will reload & ask if you want to enter setup mode • Answer NO 4: Enter the privileged mode Router>enable Router#

  18. Recovering Passwords 5: Copy the startup-config to running-config Router#copy startup-config running-config 6: Change the password Router#config t Router(config)#enable secret cisco 7: Reset the configuration register to the default value Router(config)#config-register 0x2102 8: Reload the router

  19. Backing up & Restoring the Cisco IOS • Before you upgrade….. • Copy the existing IOS to a TFTP host! • Verify Flash Memory Router#sh flash System flash directory: File Length Name/status 1 8121000 c2500-js-1.112-18.bin [8121064 bytes used, 8656152available, 16777216total] 16384K bytes of processor board System flash (Read ONLY) Router#

  20. Restoring or Upgrading the Cisco IOS #1: Ensure you have good connectivity to the TFTP host Router#ping 192.168.0.120 #2: Copy the IOSfrom the TFTP host toflash Router#copy tftp flash • This copies the new IOS, currently in the default directory of the TFTP server, to NVRAM where it will become the operating system for the router, switch or other Cisco device being upgraded. • The TFTP host must have a default directory specified • Copying the IOS from a TFTP host to flash requires a router reboot 20 / 265

  21. Backing up the Cisco IOS #1: Ensure you have good connectivity to the TFPT host Router#ping 192.168.0.120 #2: Copy the IOS from flash to the TFTP host Router#copy flash tftp • This command copies the contents of flash (the oldIOS version) to the TFTP host. • The TFTP host must have a default directory specified

  22. Backing up the Configuration 1: Verify the Current Configuration Router#sh run 2: Verify the Stored Configuration Router#sh start • Verify available memory 3: Copy running-config to NVRAM Router#copy run start Router#sh start The configuration you are currently running becomes the config that you will now boot to, after copying it to NVRAM, the startup config. 4: Copy running-config to a TFTP host Router#copy run tftp • A second backup

  23. Restoring the Configuration • Used when… • You need to copy the startup-config to the running-config • Errors made in editing the running-config • Changes made at the TFTP host need to be copied to the running-config or startup-config Router#copy tftp run or Router#copy tftp start • NOTE: The configuration file is ASCII. Any text editor will enable changes • Erasing the Configuration Router#erase startup-config Note: When the router reboots it will be in setup mode • See Supp Power Point 2 for recovering the Configuration using Xmodem: • “Download using Xmodem from rommon >”

  24. Cisco IOS File System • Cisco has a file system called IFS that allows you to work with files and directories just as you would from a DOS prompt. • Some IFS commands use URLs as part of the command syntax. • This link is to “Cisco IOS File System Command Syntax” • http://www.cisco.com/en/US/docs/ios/12_3/configfun/command/reference/cfrintro.html#wp1071821 • Below are some tables showing examples of the IFS:

  25. Cisco IOS File System

  26. Cisco IOS File System

  27. Cisco IOS File System • The limitations of the IFS are, of course, that it is simply a tool to carry out some fairly basic tasks: copying files, transferring files, working with specific types of memory found in routers and switches, etc. But within these parameters, it does have some benefits: • One of the benefits is that the file system’s user interface is universal — it’s not platform specific. You get to use the same syntax for all your commands on all of your routers. • Another benefit is that it cuts down on all those obligatory prompts for a lot of the commands. • If you want to enter a command, all you have to do is type all the necessary infostraight intothe command line. • if you want to copy a file to an FTP server, all you do is: • first indicate where the desired source fileis on your router • pinpoint where the destination file is on the FTP server • determine the username and password you’re going to use, and • type it all in on one line!

  28. Using Cisco Discovery Protocol (CDP) • A Cisco proprietary protocol • Designed to collect information about directly attached & remote devices • Hardware information • Protocol information • Useful in troubleshooting & documenting the network

  29. Getting CDP Timers & Holdtime Information • Configuration: • CDP Timer: How often CDP packets are transmitted to all active interfaces • CDP Holdtime: The amount of time that the device will hold packets received from neighbor devices Router#sh cdp Global CDP information Sending CDP packets every 60 seconds Sending a value of 180 seconds Router#config t Router(config)#cdp timer 90 Router(config)#cdp holdtime 240

  30. Getting Neighbor Information • Shows information about directly connected devices • CDP packets are not passed througha Cisco switch • Can only see what is directly attached Router#sh cdp nei (“nei” stands for “Neighbor”, i.e., “directly attached” devices). or Router#sh cdp neighbor detail • Detailed information; hostname, IP address, etc

  31. Getting Interface Traffic & Port Information • Interface Traffic Information: • CDP packets sent & received • Errors with CDP Router# sh cdp traffic • Port & Interface Information: • Encapsulation on the line • Timer & Holdtime for each interface Router# sh cdp interface

  32. Using Telnet • A virtual terminal protocol • Part of the TCP/IP suite • Allows connections to remote devices • Gather information • Run programs Note: The VTY passwords must be set on the routers in order for them to allow a telnet session.

  33. Using Telnet • SettingVTY passwords: RouterB#config t - to global config mode RouterB(config)#line vty 0 4 - to get to line-config mode, for telnet RouterB(config)#login - sets the state to enter login PW RouterB(config)#password cisco - set the login PW as “cisco” RouterB(config)#^Z - brings you back to privileged mode RouterA#172.16.10.2 - entering just an IP addr tries telnet Trying 172.16.10.2 … Open User Access Verification Password: RouterB>

  34. Setting VTY password: RouteBr#config t RouterB(config)#line vty 0 4 RouterB(config)#login RouterB(config)#password cisco RouterB(config)#^Z RouterA#172.16.10.2 Trying 172.16.10.2 … Open User Access Verification Password: RouterB> Remember…. VTY password is the user mode(>) password - not the enable mode (#) password With no enable/enable secret password set, the following happens: RouterB>en % No password set RouterB> This equates to good security! (in other words, with telnet, you MUST have a password set in order to access the utility!) Using Telnet

  35. Telnet Commands • Telnetting into Multiple Devices Ctrl+Shift+6 (release) X • Checking Telnet Connections Router#sh sessions • Checking Telnet Users Router#sh users • Closing Telnet Sessions RouterB>exit RouterB>disconnect

  36. Resolving Hostnames • To use a hostname rather than an IP address to connect to a remote host a device must be able to translate the hostname to an IP address • Build a host table on each router • Build a Domain Name System (DNS) server

  37. Building a Host Table • Provides name resolution only on the router on which it is built [ip host name tcp_port_number ip_address]u Router(config)#ip host RouterB 172.16.10.2 Router(config)#ip host switch 192.168.0.148 Router#sh hosts • Default TCP port number: 23 Router#RouterB RouterB#(Ctrl+Shift+6) (X) Router#switch

  38. Using DNS to Resolve Names • Used when you have many devices on your network • Making DNS work… • ip domain-lookup • Turned on by default • ip name-server • Sets the IP address of the DNS server (up to 6 each) • ip domain-name • Appends the domain name to the hostname Ex: RouterA.neversail.navy.mil

  39. Checking Network Connectivity • Ping • Displays the minimum, average, & maximumtimes it takes for a ping packet to find a specified system + return Router#ping RouterB • Trace • Shows the path a packet takes to get to a remote device Router#trace RouterB

  40. Summary • Go through all the written and review questions • Go through the answers with the class 40

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