In this chapter they use the Cisco Internetwork Operating System to interconnect and configure the computers, switches, routers into an Ethernet LAN. The Cisco IOS services are generally accessed using a command line interface (CLI). T here is several ways to access the CLI environment. The most usual methods are: Console; Telnet or SSH; and AUX port. When the networking services have not been started or have failed, the console port is frequently used to contact a device.
Samples of console use are:
· The initial configuration of the network device
· Disaster recovery procedures and troubleshooting where remote access is not possible
· Password recovery procedures
Telnet session needs dynamic networking services on the device. Another way for remotely accessing a CLI session is to telnet to the router. The Secure Shell (SSH) protocol is a more safe way for remote device access. This protocol gives the composition for a distant login similar to Telnet, but it utilizes safer network services.
Other way to establish a CLI session distantly is using a telephone dialup connection using a modem connected to the router's AUX port. The same as to the console connection, this other way doesn’t involve any networking services to be configured or existing on the device.
Startup Configuration File (startup-config) is used at some point in system startup to organize the device. The startup configuration file or startup-config file is stored in non-volatile RAM (NVRAM).
Running Configuration - Changes to the running configuration will directly influence the function of the Cisco device.
Router(config)# - the default prompt for the global configuration mode on a router
The two primary modes of operation are:
User EXEC- this is useful for some basic operations but still it has limited capabilities. That’s why it only allows a limited number of basic monitoring commands.
The user EXEC mode is identified by the CLI prompt that ends with the > symbol.
SAMPLE: Switch> -
Privileged EXEC – Its mode can be identified by the prompt ending with the # symbol
- It doesn’t require authentication. But still a good practice to guarantee that the authentication is configured.
SAMPLE: Switch# -).
Enable mode – This is the term used to represent the privileged exec mode.
disable command - This is used to exit in the privileged EXEC mode and to the return in user EXEC mode.
The basic IOS command is first the prompt, then the command, space and lastly the argument or keyword.
Commands are used to execute an action, and the
Keywords are used to classify where or how to complete the command.
Summary of IOS features and commands:
User EXEC Mode
enable - Enter Privileged EXEC mode
Privileged EXEC Mode
copy running-config startup-config - Copy the active configuration to NVRAM.
copy startup-config running-config - Copy the configuration in NVRAM to RAM.
erase startup-configuration - Erase the configuration located in NVRAM.
ping ip_address - Ping to that address.
traceroute ip_address - Trace each hop to that address.
show interfaces - Display statistics for all interfaces on a device.
show clock - Show the time set in the router.
show version - Display currently loaded IOS version, hardware, and device information.
show arp - Display the ARP table of the device.
show startup-config - Display the saved configuration located in NVRAM.
show running-config - Display the contents of the currently running configuration file.
show ip interface - Display IP statistics for interface(s) on a router.
configure terminal - Enter terminal configuration mode.
Terminal Configuration Mode
hostname hostname - Assign a host name to device.
enable password password - Set an unencrypted enable password.
enable secret password - Set a strongly encrypted enable password.
service password-encryption - Encrypt display of all passwords except secret.
banner motd# message # - Sets a message-of-the-day banner.
line console 0 - Enter console line configuration mode.
line vty 0 4 - Enter virtual terminal (Telnet) line configuration mode.
interface Interface_name - Enter interface configuration mode.
Line Configuration Mode
login - Enable password checking at login.
password password - Set line password.
Interface Configuration Mode
ip address ip_address netmask - Set interface IP address and subnet mask.
description description - Set interface description.
clock rate value - Set clock rate for DCE device.
no shutdown - Set interface to up.
shutdown - Administratively set interface to down.
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