IOS-Basic Configuration
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The document provides instructions on basic router configuration and commands. It covers topics like: - Connecting to a router via terminal emulation programs and setting terminal settings - Gathering information about the router and its interfaces - Configuring basic settings like hostname, passwords, and descriptions - Viewing, saving and managing configurations - Recovering lost passwords by changing the configuration register
IOS-Basic Configuration
- 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 Shell 1. set your hostname: hostname ccna 2. Set domain name: ip domain-name ccna.com 3. Set username: username haitham password 5678 4. Generate encryption key: crypto key generate rsa general-keys modulus 1024 5. Ssh version 2 6. 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 Sequence When router boots up, it performs sequence of steps, called: Boot Sequence. 1. Router performs POST 2. Locate IOS. Bootstrap loads IOS.
- 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 recovery 1. Boot the router and interrupt the boot sequence by performing a break, which will take the router into ROM monitor mode. 2. Change the configuration register to turn on bit 6 (with the value 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