Cisco Router Basic Configuration

© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
ITE PC v4.0
Chapter 1 1
CISCO Router
Basic Configuration
-Mr. Dan Ablong
• What is Cisco?
• Introduction to Routing and Packet Forwarding
• Introduction to Packet Tracer (Network Simulator)
• Router Configuration
• Summary

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Chapter 1 2
What is CISCO?

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Chapter 1 3© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
CISCO System Inc.
is an American multinational corporation headquartered
in San Jose, California, United States, that designs,
manufactures, and sells networking equipment. The
name "Cisco" was derived from the city name, San
Francisco, which is why
the company's engineers
insisted on using the lower
case "cisco" in the early
days.

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CISCO Networking

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DID YOU KNOW?

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Chapter 1 6
Introduction to
Routing and Packet
Forwarding

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Objectives
 Identify a router as a computer with an OS and
hardware designed for the routing process.
 Demonstrate the ability to configure devices and
apply addresses.
 Describe the structure of a routing table.
 Describe how a router determines a path and
switches packets

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Router as a Computer
 Describe the basic purpose of a router
-Computers that specialize in sending packets over the data
network. They are responsible for interconnecting networks by
selecting the best path for a packet to travel and forwarding
packets to their destination
 Routers are the network center
-Routers generally have 2 connections:
-WAN connection (Connection to ISP)
-LAN connection

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 Data is sent in form of packets between 2 end devices
 Routers are used to direct packet to its destination

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 Routers examine a packet’s destination IP address and
determine the best path by enlisting the aid of a routing
table

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 Router components and their functions”
CPU - Executes operating system instructions
Random access memory (RAM) - Contains the running copy of
configuration file. Stores routing table. RAM contents lost when power
is off
Read-only memory (ROM) - Holds diagnostic software used when
router is powered up. Stores the router’s bootstrap program.
Non-volatile RAM (NVRAM) - Stores startup configuration. This may
include IP addresses (Routing protocol, Hostname of router)
Flash memory - Contains the operating system (Cisco IOS)
Interfaces - There exist multiple physical interfaces that are used to
connect network. Examples of interface types:
-Ethernet / fast Ethernet interfaces
-Serial interfaces
-Management interfaces

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 Router Interface is a physical connector that enables a
router to send or receive packets
 Each interface connects to a separate network
 Consist of socket or jack found on the outside of a router
 Types of basic router interfaces:
-Ethernet
-Fastethernet
-Serial

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Chapter 1 13
Introduction to
Packet Tracer
(Cisco Network Simulator)

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Cisco Packet Tracer - is a powerful network simulation
program that allows students to experiment with
network behavior and ask “what if” questions.

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Chapter 1 15
Router
Configuration

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Configure Devices and Apply Addresses
 Implementing Basic Addressing Schemes
 When designing a new network or mapping an existing
network you must provide the following information in
the form of a document:
-Topology drawing that Illustrates physical connectivity
–Address table that provides the following information:
Device name
Interfaces used
IP addresses
Default gateway

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Basic Router Configuration
 A basic router configuration should contain the following:
-Router name - Host name should be unique
-Banner - At a minimum, banner should warn against
unauthorized use
-Passwords - Use strong passwords
-Interface configurations - Specify interface type, IP address
and subnet mask. Issue no shutdown command. If DCE serial
interface, issue a clock rate command.
 After entering in the basic configuration the following tasks should
be completed
-Verify basic configuration and router operations.
-Save the changes on a router

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 Verify Basic Router Configuration
-Issue the show running-config command
-Save the basic router configuration by Issuing the copy
running-config startup-config command
-Additional commands that will enable you to further verify
router configuration are:
Show running-config - Displays configuration currently in
RAM
Show startup-config - Displays configuration file NVRAM
Show IP route - Displays routing table
Show interfaces - Displays all interface configurations
Show IP int brief - Displays abbreviated interface
configuration information

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Routing Table Structure
 Routing Table is stored in ram and contains information
about:
Directly connected networks - this occurs when a device is
connected to another router interface
Remotely connected networks - this is a network that is not
directly connected to a particular router
Detailed information about the networks include source of
information, network address & subnet mask, and Ip address of
next-hop router
 Show ip route command is used to view a routing table

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 Static routes in the routing table
-Includes: network address and subnet mask and IP address of
next hop router or exit interface
-Denoted with the code S in the routing table
-Routing tables must contain directly connected networks used
to connect remote networks before static or dynamic routing
can be used
 When to use static routes
-When network only consists of a few routers
-Network is connected to internet only through one ISP
-Hub & spoke topology is used on a large network

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 Connected and Static routes

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 Dynamic routing protocols
-Used to add remote networks to a routing table
-Are used to discover networks
-Are used to update and maintain routing tables
 Automatic network discovery
-Routers are able discover new networks by sharing routing
table information

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 Maintaining routing tables
-Dynamic routing protocols are used to share routing information with
other router & to maintain and up date their own routing table.
 IP routing protocols. Example of routing protocols include:
-RIP
-IGRP
-EIGRP
-OSPF

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 Routing Table Principles
-3 principles regarding routing tables:
Every router makes its decisions alone, based on the
information it has in its routing table.
Different routing table may contain different information
 A routing table can tell how to get to a destination but not
how to get back

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 Effects of the 3 Routing Table Principles
-Packets are forwarded through the network from one router
to another, on a hop by hop basis.
-Packets can take path “X” to a destination but return via
path “Y”.

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Summary
 Routers are computers that specialize in sending data over a network.
 Routers are composed of:
-Hardware i.e. CPU, Memory, System bus, Interfaces
-Software used to direct the routing process
IOS
Configuration file
 Routers need to be configured. Basic configuration consists of:
-Router name
-Router banner
-Password(s)
-Interface configurations i.e. IP address and subnet mask
 Routing tables contain the following information
-Directly connected networks
-Remotely connected networks
-Network addresses and subnet masks
-IP address of next hop address

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Chapter 1 27
Summary

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Summary
 Routers determine a packets path to its destination by
doing the following
Receiving an encapsulated frame & examining destination
MAC address.
If the MAC address matches then Frame is de-encapsulated
so that router can examine the destination IP address.
If destination IP address is in routing table or there is a static
route then Router determines next hop IP address. Router will
re-encapsulate packet with appropriate layer 2 frame and send
it out to next destination.
Process continues until packet reaches destination.
Note - only the MAC addresses will change the source and
destination IP addresses do not change.

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Cisco Router Basic Configuration

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