Cisco IOS

 Let's start out by discussing some of the base CISCO devices configuration commands:

To configure a CISCO device, connect to the CONSOLE port using a ROLLOVER cable. If you're on a Windows system, on PuTTY, select Serial, set baud rate to 9600 from Device manager of the computer, figure out which COM port is connected. You would be presented with a user-mode with a command line display as follows:

Switch>

The first thing to know is that you can type enter without any text without any consequences on the command line. Second, if you'd like to get a list of commands that you can enter at any screen or if you're unsure of how to proceed further with any command, use the '?' to get a list of successive commands.

Command 1 -> Switch> enable

The above 'enable' command takes you to the privileged-mode from the user-mode.

Command 2 -> Switch# configure terminal

You can use tab to complete the command or view a list of commands starting with what you have typed down. 'configure terminal' or 'conf t' command takes you to the global configuration mode. Think of different modes as doors leading to different rooms and each room lets you configure a certain setting.

Let's see how to perform 10 actions:

1. Set Hostname to VAN-RT01

Switch> enable

Switch# conf t

Switch(config)# hostname VAN-RT01

2. Set IP address to 10.0.0.1 with a subnet mask of 255.255.255.0 on FastEthernet0/1

Switch> enable

Switch# conf t

Switch(config)# interf fa0/1

Switch(config-if)# ip addr 10.0.0.1 255.255.255.0

3. Activate the above interface

Switch> enable

Switch# conf t

Switch(config)# interf fa0/1

Switch(config-if)# no shutdown

4. Set a login banner

Switch> enable

Switch# conf t

Switch(config)# banner motd % 

Multi-line banner

%

5. Set synchronous logging on console

Switch> enable

Switch# conf t

Switch(config)# line console 0

Switch(config-line)# logging synchronous

Switch(config-line)# do show running config

NOTE: Use the word 'do' to run a command belonging to another mode without having to switch mode.

6. Set a console password as 'cisco'

Switch> enable

Switch# conf t

Switch(config)# line console 0

Switch(config-line)# password cisco

Switch(config-line)#login

7. Secure the system such that password 'cisco' is required to access the privileged mode

Switch> enable

Switch# conf t

Switch(config)# enable secret cisco

8. Set password 'cisco' for Telnet connections to the device

Switch> enable

Switch# conf t

Switch(config)# line vty 0 4

Switch(config)# password cisco

Switch(config)# login

NOTE: Remember that setting password without the login line is meaningless since everyone lands at the user-mode directly.

9. No domain lookup -> If you enter incorrect commands, this will save you time.

Switch> enable

Switch# conf t

Switch(config)# no ip domain-lookup

10. Encrypt all passwords

Switch> enable

Switch# conf t

Switch(config)#service password-encryption

BONUS -> 11. Save settings

Switch> enable

Switch# wr


---


One thing to note with Cisco IOS is that when you're typing commands, you're editing the running-config. The running-config gets stored in the RAM which is a volatile type of storage. If you would like to persist the changes across reboots, you need to save the changes to the startup-config. You can do it with the following command:

Switch# copy running-config startup-config

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