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IOS-Basic Configuration
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IOS-Basic Configuration


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  • 1. Chapter 6 IOS
  • 2. Basic Configuration• Hyper Terminal• Included with Windows – Baud Rate: 9600 – Data Bits: 8 – Parity: None – Stop Bits: 1 – Flow Control: None
  • 3. Other Terminal Programs• Hyperterm• Teraterm• Minicom• securecrt
  • 4. Getting Involved• Router# clock set 11:15:11 25 april 2011• Show history• Show terminal• Terminal history size ?
  • 5. Gathering Basic Information• Show version
  • 6. Basic Configuration• Hostname <name>• Banner motd x unauthorized access prohibited x• Enable password• Enable secret
  • 7. Auxiliary Password• Conf t• Line aux 0• Password 5678• login
  • 8. Console Password• Line console 0• Password 5678• Login• Additional commands – Exec-timeout ? – Logging synchronous
  • 9. Telnet Password• Line vty 0 ?• Password 5678• login
  • 10. Secure Shell1. set your hostname: hostname ccna2. Set domain name: ip domain-name ccna.com3. Set username: username haitham password 56784. Generate encryption key: crypto key generate rsa general-keys modulus 10245. Ssh version 26. Line vty 0 ?7. Transport input ssh telnet
  • 11. Encrypting Passwords• Show running-config• Service password-encryption• No service password-encryption
  • 12. Descriptions• Conf t• Interface• Description bla bla bla• Do show run – What does do mean?
  • 13. Router Interfaces• Move through interfaces• Move from interface to another
  • 14. Bringing Up an Interface• Conf t• Interface ?• No shutdown• Ip address # #
  • 15. Using the pipe |• Pipe means: Output Modifier• Show run | begin interface• Show ip route | include #
  • 16. Serial Interface Commands• DCE vs. DTE ‘find the clock symbol’• Add clocking to DCE only – Does it really matter?• Conf t• Int serial ?• Clock rate ?• Show controllers – Command that shows DCE connection 
  • 17. Viewing, Saving, and Erasing Configurations• Show running-config• Show startup-config• Copy running-config startup-config• Erase start-up config• Reload – Take care • Erase running-config
  • 18. Verifying Settings• Ping #destination-ip• Ping – Called: extended ping• Traceroute #destination-ip – No map this time • telnet #destination-ip• Show interface #interface-id• Show ip interface• Show ip interface brief• Show protocols• Show controllers #serial-id
  • 19. Internal Components• Bootstrap: – Stored in ROM, used to bring router up during initialization. Boot the router, load the IOS.• POST: – Stored in ROM, used to check the basic functionality of the router hardware and determines which interfaces are present
  • 20. Internal Components• RAM: – Hold packet buffers, ARP cache, routing tables, running-config, most routers expand IOS from flash to RAM on boot• ROM: – Start and maintain the router. Hold Boot Strap, and POST• Flash Memory: – Store CISCO IOS by default. It is not erased when router is reloaded.
  • 21. Internal Components• NVRAM: – Hold the router and switch configuration. Not erased when device is reloaded. Does not store IOS. Configuration Register is stored in NVRAM.• Configuration Register – Control how the router boots up. This value can be found as the last line in #show version. Default: 0x2102 -> load IOS from flash and load configuration from NVRAM
  • 22. Router Boot SequenceWhen router boots up, it performs sequence ofsteps, called: Boot Sequence.1. Router performs POST2. Locate IOS. Bootstrap loads IOS.
  • 23. Configuration Register Bits
  • 24. Changing Configuration Register Value• Main Reasons: – Force system into the ROM monitor mode – Select boot source – Enable or disable Break function – Control Broadcast addresses – Set console terminal baud rate – Load OS from ROM – Enable booting from TFTP
  • 25. Important• Don’t try this on real device… – Unless you have to!
  • 26. • Router(config)#config-register 0x2101• Show version• Show flash• Config-register 0x2102• Reload• Now What?
  • 27. Recovering Passwords• The default configuration register value is 0x2102, meaning that bit 6 is off. With the default setting, the router will look for and load a router configuration stored in NVRAM (startup-config). To recover a password, you need to turn on bit 6. Doing this will tell the router to ignore the NVRAM contents. The configuration register value to turn on bit 6 is 0x2142.
  • 28. main steps to password recovery1. Boot the router and interrupt the boot sequence byperforming a break, which will take the router into ROMmonitor mode.2. Change the configuration register to turn on bit 6 (with thevalue 0x2142).3. Reload the router.4. Enter privileged mode.5. Copy the startup-config file to running-config.6. Change the password.7. Reset the configuration register to the default value.8. Save the router configuration.9. Reload the router (optional).
  • 29. 1. Break the Boot Sequence• Ctrl + Break• While loading!• Rommon: Rom Monitor Mode
  • 30. Configure the Register• Cisco ISR/2600: – Rommon 1> confreg 0x2142 – Rommon 1> reload• Cisco 2500: – >o/r 0x2142
  • 31. Reload the Router• Cisco ISR/2600: – Rommon 1> reset• Cisco 2500: – >I
  • 32. Change Configuration• Copy startup-config running-config• Copy start run – Same command 
  • 33. Reset Configuration• Conf t• Config-register 0x2102