CCNA Guide to Cisco
Networking Fundamentals
Fourth Edition
Chapter 5
Router and IOS Basics
Objectives
• Describe the benefits of network segmentation with
routers
• Understand the elements of the Cisco router user
interface
• Configure the HyperTerminal program to interface
with the Cisco router
• Describe the various router configuration modes
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Objectives (continued)
• Describe the various router passwords
• Understand the enhanced editing features of the
Cisco IOS
• Compare router components to typical PC
components
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Benefits of Routing
• Routers provide
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Packet filtering
Connections between local networks
Traffic control
Wide area network (WAN) connections
• Routers operate at the Network layer of the OSI
reference model
– Because of Network layer addressing, routers can
direct packets to both local and remote segments
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Cisco Router User Interface
• Cisco Internetwork Operating System (IOS)
– Provides a command-line interface (CLI)
• Allows network operators to check the status of the
router and network administrators to manage and
configure the router
• You can access a router in several different ways
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–
–
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Console port (also known as the console)
Auxiliary port (AUX)
Virtual terminals (VTY)
Trivial File Transfer Protocol (TFTP) server
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Connecting via Terminal Programs
• When configuring the router through the console or
AUX ports
– You must first make the physical connection
– Then, you can access the router through a terminal
program
• Steps to configure HyperTerminal:
– Open the HyperTerminal application
– Click File on the menu bar, and then click New
Connection
– Enter a name for the connection
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Connecting via Terminal Programs
(continued)
• Steps to configure HyperTerminal: (continued)
– Configure how you will connect to the router via the
Connect To dialog box
• If you are connecting to the router through the AUX
port, you would provide the router phone number here
• If connecting to the router through the console port,
click the “Connect using” list box and choose the COM
port to which the RJ-45 to DB-9 connector is attached
– Configure the following settings for the COM port: Bits
per second, 9600; Data bits, 8; Parity, None; Stop
bits, 1; Flow control, None
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System Configuration Dialog
• If the router has not been configured previously, or if
the startup file has been erased
– The Cisco IOS will prompt you to run the initial
configuration dialog after the router boots
• The system configuration dialog presents a series of
prompts that guide you through the initial
configuration for the router
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User Interface
• The initial prompt consists of two parts:
– The host name of the router followed by the greater
than symbol (>)
– Default: router>
• User EXEC mode (or user mode)
– When the prompt displayed is the greater than
symbol
– Network operator can check router status and review
several of the router settings
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User Interface (continued)
• The question mark activates context-sensitive
Help on the Cisco router
• User mode does not allow you to configure the
router
– To do this, you must go into the privileged EXEC
mode
• To enter privileged EXEC, you can type the enable
command at the user mode prompt
– Next, you may be prompted for a password
– Greater than symbol (>) changes to a pound sign (#)
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User Interface (continued)
• You can do a few things at this prompt
– Setup: the setup command will cause the router to
enter the system configuration dialog
– Copy: configurations can be copied from TFTP
servers to the router and therefore change the router
configuration
– Erase: configuration files as well as the entire IOS
can be erased
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Configuration Modes
• Global configuration mode
– Accessed by typing configure terminal at the enable
mode prompt
• Interface configuration mode
– Allows you to configure the Ethernet and serial
interfaces on your router
• Line configuration mode
– Allows you to configure the virtual terminals, console,
and AUX lines that let you access the router
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Configuration Modes (continued)
• Typing exit will take you back one level
• Typing end or pressing the Ctrl+Z keys will take you
all the way back to the enable prompt
• Often, you can discover abbreviated commands by
simply trying them
– The router will show you the point at which you
entered an incorrect character
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Configuration Modes (continued)
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Plethora of Passwords
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Plethora of Passwords (continued)
• Enable Password and Enable Secret Password
configuration
– You can set both passwords from the global
configuration mode prompt
– Because it is encrypted, the enable secret password
is more secure than the enable password
– You can type no enable secret and no enable
password at the global configuration mode prompt
• To remove the enable secret and enable passwords
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Plethora of Passwords (continued)
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Plethora of Passwords (continued)
• Setting Line passwords
– Line passwords are the first line of defense against
unauthorized intrusion into the router
– You can set passwords for each line used to
configure the router
– Configure the console line password
• Enter line configuration mode
– You can also configure passwords on the five virtual
terminal lines that exist on every router
• In much the same way as on the console port
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Plethora of Passwords (continued)
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Plethora of Passwords (continued)
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Plethora of Passwords (continued)
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Enhanced Editing
• By default, the router supports enhanced editing
features that allow you to modify lengthy commands
• The enhanced editing commands let you jump to the
beginning or end of a command line
• You can also jump forward or back, character by
character, or word by word
• You can turn off the enhanced editing features by
typing terminal no editing at either the user
EXEC or the privileged EXEC prompts
– You can turn on terminal editing by typing terminal
editing
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Enhanced Editing (continued)
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Command History
• Command history
– Allows you to retrieve previously typed commands
• You can see up to 10 previously typed commands
by typing show history
– From either the user EXEC or privileged EXEC
mode
• To modify the number of commands stored by the
router, you can use the terminal command
– Up to 256 previous commands
– Type terminal history size n
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Configuring Router Identification
• Router host name
– Default host name is router
– To set the router host name, type hostname followed
by the name that you want to set
• Configure a banner
– A banner is a message that you can configure to
display each time someone attempts to log in to the
router
– Enter global configuration mode by typing config t
• Then type banner motd, followed by a space and a
delimiting character
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Configuring Router Identification
(continued)
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Configuring Router Identification
(continued)
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Configuring Router Identification
(continued)
• Configure an interface description
– Use the description command
– The interface description helps you remember which
network the interface services
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Configuring the Time and Date
• Use the clock set command in enable mode to
configure the time
– You must be in global configuration mode to configure
the time zone
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Router Components
• This section discusses the hardware elements of the
router:
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ROM
Flash memory
NVRAM
RAM/DRAM
Interfaces
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ROM
• Read-only memory (ROM)
– Loads the bootstrap program that initializes the
router’s basic hardware components
– Not modified during normal operations, but it can be
upgraded with special plug-in chips
• The content of ROM is maintained even when the
router is rebooted
• The ROM monitor firmware runs when the router is
turned on or rebooted
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Flash Memory
• Flash memory
– A type of erasable, programmable, read-only memory
(EPROM)
– Not typically modified during normal operations
• However, it can be upgraded or erased when necessary
• The content of flash memory is maintained even
when the router is rebooted
• Flash memory
– Contains the working copy of the current Cisco IOS
– Is the component that initializes the IOS for normal
router operations
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NVRAM
• Nonvolatile random access memory (NVRAM)
– A special type of RAM that is not cleared when the
router is rebooted
• The startup configuration file for the router is stored
in NVRAM by default
– This is the first file created by the person who sets up
the router
• The Cisco IOS uses the configuration file in NVRAM
during the router boot process
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RAM/DRAM
• Random access memory (RAM)
– Also known as dynamic random access memory
(DRAM)
– A volatile hardware component
– Its information is not maintained in the event of a
router reboot
• Changes to the router’s running configuration take
place in RAM/DRAM
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RAM/DRAM (continued)
• The IOS contains commands to view each of the
router’s components
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show
show
show
show
Copy
running-config
memory
buffers
startup-config
running-config startup-config
• Abbreviated as Copy run start
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Interfaces
• A router can ship with a variety of configurable
interfaces
– A common interface is Ethernet0
• Other types of interfaces include:
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Token Ring
Basic Rate Interface (BRI)
Asynchronous Transfer Mode (ATM)
Fiber Distributed Data Interface (FDDI)
Channel Interface Processor (CIP) for Systems
Network Architecture (SNA)
– High-Speed Serial Interface (HSSI)
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Summary
• Cisco routers use the Cisco IOS to provide an
interface for network operators and administrators
• The first mode entered is user EXEC (router>
prompt) and the next mode is privileged EXEC
(router# prompt)
• In user EXEC, you can accomplish basic tasks
• To actually configure the router, privileged EXEC
mode must be accessed
• The privileged EXEC mode is often called enable
mode
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Summary (continued)
• The enable, enable secret, and VTY passwords are
set during initial configuration if the system
configuration dialog is used
• When configured, the enable secret password
supersedes the enable password
• The components of a router include ROM, flash
memory, NVRAM, RAM/DRAM, and interfaces
• ROM stores a limited version of the Cisco IOS and
routines for checking the hardware during system
boot
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Summary (continued)
• Flash memory stores the Cisco IOS that is loaded
by default during system boot
• NVRAM stores the startup copy of the router
configuration file that is loaded by default during
system boot
• RAM/DRAM stores the working copy (running
configuration) of the router configuration
• Interfaces provide connectivity to various types of
LANs and WANs
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