Chapter 10


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Chapter 10

  1. 1. Cisco Basics, IOS & Network Basics CMC Limited
  2. 2. Objectives • Describe router elements • Configure router passwords, identification, and banner • Use the context-sensitive help facility • Use the command history and editing features • Perform the initial router configuration • Use show commands to display basic network • operational features • Describe router start-up sequence • Establish connectivity from a host to the appropriate • network device to perform configuration tasks • In accordance with open standards, interconnect • network devices • Differentiate between routed and routing protocols CMC Limited
  3. 3. Cisco Router IOS The Cisco Internetwork Operating System (IOS) is the kernel of Cisco routers and most switches. Almost all Cisco routers run the same IOS, in contrast to only about half of their switches. The IOS was created to deliver network services and enable networked applications. You can access the Cisco IOS through the console port of a router, from a modem into the Aux port, or even through Telnet. CMC Limited
  4. 4. Internal Components of a Cisco Router In order to configure and troubleshoot a Cisco internetwork, one needs to know the major components of Cisco routers and understand what these components do.The Router Boot SequenceWhen a router boots up, it performs a series of steps, calledthe boot sequence, to test the hardware and load thenecessary software. CMC Limited
  5. 5. Managing Configuration Registers All Cisco routers have a 16-bit software register, which is written into NVRAM .Understanding the ConfigurationRegister Bits The 16 bits of the configuration register are read from 15 to 0, from left to right. The default configuration setting on Cisco routers is 0x2102. CMC Limited
  6. 6. Managing Configuration Registers contd..Checking the Current Configuration RegisterValue You can see the current value of the configuration register by using the show version command (sh version or show ver for short), CMC Limited
  7. 7. Managing Configuration Registers contd..Changing the Configuration Register One can change the configuration register value to modify how the router boots and runs. One can change the configuration register by using the config-register command. CMC Limited
  8. 8. Managing Configuration Registers contd..Recovering Passwords If you are locked out of a router because you forgot the password, you can change the configuration register to help you recover. The default configuration register value is 0x2102, which means that bit 6 is off. CMC Limited
  9. 9. Managing Configuration Registers contd..Interrupting the Router Boot Sequence The first step is to boot the router and perform a break, by pressing the Ctrl+Break key combination when using HyperTerminal.Changing the Configuration Register You can change the configuration register by using the config-register command. To turn on bit 6, use the configuration register value 0x2142. CMC Limited
  10. 10. Managing Configuration Registers contd..Reloading the Router and EnteringPrivileged Mode At this point, you need to reset the router. • From the 2600 series router, type reset. • From the 2500 series router, type I (for initialize).Viewing and Changing the ConfigurationAlthough you cannot view the enable secret setting for thepassword, you can change the password, by: config t enable secret rahul CMC Limited
  11. 11. Managing Configuration Registers contd..Resetting the Configuration Register andReloading the RouterAfter you are finished changing passwords, set theconfiguration register back to the default value with theconfig-register command. config t config-register 0x2102 Finally, save the new configuration with a copy running-config startup-config and reload the router. CMC Limited
  12. 12. Cisco Router User InterfaceYou can connect to a Cisco router to configure the router,verify the configuration, and check statistics.There are different ways to do this, but most often, the firstplace you would connect to is the console port.But you can also connect to a Cisco router through anauxiliary port, which is really the same thing as a consoleport so you can use it as one. CMC Limited
  13. 13. Cisco Router User Interface contd..Bringing Up a Router When you first bring up a Cisco router, it will run a power-on self-test (POST), and if that passes, it will then look for and load the Cisco IOS from Flash memory, if a file is present. Flash memory is an electronically erasable programmable read-only memory [EEPROM]. The IOS then proceeds to load and then look for a valid configuration – the startup- config – thats stored by default in nonvolatile RAM (NVRAM). CMC Limited
  14. 14. Setup Mode There are two options when using setup mode: Basic Management and Extended Setup. Basic Management setup configures only enough connectivity for management of the system.Command-Line Interface The command-line interface (CLl) is really the best way to configure a router.Logging into the Router After the interface status messages appear and you press Enter, the Router> prompt will appear. CMC Limited
  15. 15. Command-Line Interface contd..Overview of Router ModesTo configure from a CLI, you can make global changes tothe router by typing configure terminal (or config t for short),which puts you in global configuration mode and changeswhats known as the running-config.CLI PromptsIts really important that you understand the differentprompts you can find when configuring a router. Alwayscheck your prompts before making any changes to a routersconfiguration! CMC Limited
  16. 16. Command-Line Interface contd..Editing and Help FeaturesYou can use the Cisco advanced editing features to helpyou configure your router.Real world ScenarioThere are a couple of editing features that are used quiteoften; some are not used as much, if at all. Understand thatCisco didnt make these up; these are just old Unixcommands. However, Ctrl+A is really helpful to negate acommand. CMC Limited
  17. 17. Command-Line Interface contd..Gathering Basic Routing Information The show version command will provide basic configuration for the system hardware as well as the software version, the names and sources of configuration files, and the boot images.Setting Passwords There are five passwords used to secure your Cisco routers. The first two passwords are used to set your enable password, which is used to secure privileged mode. The other three are used to configure a password when user mode is accessed either through the console port, the auxiliary port, or via Telnet. CMC Limited
  18. 18. Command-Line Interface contd..Encrypting Your Passwords Only the enable secret password is encrypted by default, youll need to manually configure the user-mode and enable passwords.Banners A good reason for having a banner is to add a security notice to users dialing into your internetwork.Router Interfaces Interface configuration is one of the most important configurations of the router, because without interfaces, a router is totally useless. CMC Limited
  19. 19. Command-Line Interface contd..Bringing Up an Interface You can turn an interface off with the interface command shutdown, and turn it on with the no shutdown command.Configuring an IP Address on anInterface you dont have to use IP on your routers, its Even though most often what people use. To configure IP addresses on an interface, use the ip address command from interface configuration mode . CMC Limited
  20. 20. Command-Line Interface contd..Serial Interface CommandsThe interface will usually be attached to a CSU/DSU type ofdevice that provides clocking for the line. But if you have aback-to-back, one end-the data communication equipment(DCE) end of the cable-must provide clocking.HostnamesYou can set the identity of the router with the host namecommand. This is only locally significant, which means ithas no bearing on how the router performs name lookups orhow the router works on the internetwork. CMC Limited
  21. 21. Command-Line Interface contd..DescriptionsSetting descriptions on an interface is helpful to theadministrator and, like the hostname, only locally significant.This is a helpful command because you can use it to keeptrack of circuit numbers.Real World ScenarioThe interface description command is very helpful if, forexample, you have many administrators and no one canremember where any interface is connected. CMC Limited
  22. 22. Command-Line Interface contd..Viewing and Saving ConfigurationsIf you run through setup mode, youll be asked if you wantto use the configuration you just created.Verifying Your ConfigurationShow running-config would be the best way to verify yourconfiguration, and show startup-config would be the bestway to verify the configuration thatll be used the next timethe router is reloaded. CMC Limited
  23. 23. Using Telnet Telnet is a virtual terminal protocol that is part of the TCP/IP protocol suite. Telnet allows you to make connections to remote devices, gather information, and run programs.Telnetting into Multiple DevicesSimultaneously If you telnet to a router or switch, you can end the connection by typing exit at any time. CMC Limited
  24. 24. Using Telnet contd..Checking Telnet ConnectionsTo see the connections made from your router to a remotedevice, use the show sessions command.Checking Telnet UsersYou can list all active consoles and VTY ports in use onyour router with the show users command. CMC Limited
  25. 25. Using Telnet contd..Closing Telnet SessionsYou can end Telnet sessions a few different ways. Typingexit or disconnect is probably the easiest and quickest. CMC Limited
  26. 26. Resolving HostnamesIn order to use a hostname rather than an IP address toconnect to a remote device, the device that you are usingto make the connection must be able to translate thehostname to an IP address.Building a Host TableA host table provides name resolution only on the router onwhich it was built CMC Limited
  27. 27. Resolving Hostnames contd..Using DNS to Resolve Names If you have many devices and dont want to create a host table in each device, you can use a DNS server to resolve hostnames.Real World Scenario If you have dozens of routers, then you dont want to build a static host table on each router. You can build one table on a DNS server. CMC Limited
  28. 28. Checking Network ConnectivityYou can use the ping and trace route commands to testconnectivity to remote devices.Using the Ping CommandTo see all the different protocols that you can use with ping,use the ping ? Command.Using the Traceroute CommandTraceroute (the traceroute command, or trace for short)shows the path a packet takes to get to a remote device. CMC Limited