Cisco Router IOS

1. Cisco Router IOS

2. What is IOS? • Cisco IOS (originally Internetwork Operating System) is the software used on the vast majority of Cisco Systemsrouters and all current Cisco network switches. (Earlier switches ran CatOS). • IOS is a package of routing, switching, internetworking and telecommunications functions tightly integrated with a multitasking operating system.

3. Connecting to a Router • Hook up the power cable to the router. • Connect the serial console cable from the router's console port (RJ-45) to the back of a PC or laptop (DB-9 Serial, "COM1 Port"). • Because HyperTerminal comes with Windows, many people use it to configure Cisco routers. To open HyperTerminal from Windows, go to Start | Programs | Accessories | Communications | HyperTerminal.

4. Create a new connection called RouterA, click OK to accept the default of using COM1, Click on Configure.Change the bits per second = 9600, data bits = 8, Parity = None, and Flow control = None. Click OKPower-on the router, and watch the boot-up sequence.

5. Router Modes • Bootstrap takes you to the router> prompt, which means you're in User Mode. You can identify User Mode by the [>] at the end of the prompt. However, you really can't accomplish anything useful in User Mode, so enter enable and press [Enter] to go to Privileged Mode. • Once in Privileged Mode, you should see the router# prompt. Like the [>] indicator for User Mode, [#] at the end of the prompt indicates that you are in Privileged Mode. This is equivalent to the Administrator account in Windows. • If the router has an assigned password, you will be asked for it when you attempt to enter Privileged Mode • You can only view things when in Privileged Mode—you can't change anything. To change something, you must be in Global Configuration Mode. To get to this mode, enter configure terminal, and press [Enter]. The prompt should now say router(config)#.

6. Navigating Cisco IOS Modes Mode Prompt Command In this example, we go from the lowest mode to the highest mode. User Mode Router> Enable Privileged Mode Router# ConfigureTerminal Global Configuration Mode Router(config)# Write /Exit In this example, we go from the highest mode to the lowest mode. Privileged Mode Router# Disable User Mode Router>

7. Router Configurations • When you enter Config mode, you are altering the configuration of the router. • The router keeps two different sets of configurations. When you first turn it on the router loads the startup configuration into memory. Now that it is loaded it is now called the running configuration, the startup configuration is the original copy. • When you make a change, it happens on the fly and is applied to the running configuration. Suppose you totally screw up and cannot even telnet to the router anymore, just unplug it and plug it back in and it will boot up off the startup configuration again. • This is a good feature in this case, but what if you made a bunch of changes, forgot to update the startup configuration and then the power goes out? You guessed it, all your work is lost. So keep in mind what you are doing and keep track of when you want to save. • Saving the running configuration is easily done with the command: • copy running-config startup-config  copy run start • And of course if you ever screw anything up but still have access to the router, you can always copy the startup configuration to the running configuration. And you do not even have to reboot.

8. Basic IOS Commands Sometimes the only way to see the entire router configuration is to dump the configuration commands. • The command: show running-config does exactly that – here’s an example….

9. ! • version 12.2 • service timestamps debug uptime • service timestamps log uptime • no service password-encryption • service udp-small-servers • service tcp-small-servers • no service single-slot-reload-enable • ! • hostname buell • ! • ... • ! • interface Ethernet0/3 • °c 2007, Hans Kruse and Carl Bruggeman 2 January 15, 2007 • no ip address • no ip proxy-arp • shutdown • ! • interface Ethernet0/4 • no ip address • no ip proxy-arp • shutdown • ! • interface Ethernet0/5 • ip address 132.235.201.40 255.255.255.128 • no ip proxy-arp • ! • ... • ! • ip classless • ip route 0.0.0.0 0.0.0.0 132.235.201.126 • ... • In this example, note that ethernet interfaces 0/3 and 0/4 are not configured, 0/5 has been set up.

10. Router Interfaces • An interface is any port that the router can use to move network traffic. • Interfaces are two types: • Ethernet • Serial • A router can have multiple interfaces, depending on what hardware is installed

11. Interface Configuration Commands • IOS has specific commands to configure an interface • Interface configuration begins from configuration mode • Enter the interface type slot/port (for Cisco 7000 series) or interface type port (for Cisco 2500 series) to enter the interface configuration mode. • Example: Router (config)#interface ethernet 0/1 • (for a serial port, you would use interface serial 0/1)

12. Interface Configuration Commands - cont’d • Enter the IP address and subnet mask of the interface using the ip address ipaddress subnetmask command. • Example, • Router (config-if)#ip address 192.168.10.1 255.255.255.0 • Step 5: Exit the configuration mode by pressing Ctrl-Z • Router(config-if)#[Ctrl-Z]