© 2007 cisco systems, inc. all rights reserved. 1 network addressing networking for home and small...

© 2007 Cisco Systems, Inc. All rights reserved. 1

Network Addressing

Networking for Home and Small Businesses – Chapter 5

Cisco Discovery Home & Small Business Chapter 5 2

Teacher Notes

It is highly recommended that the instructor begin Chapter 5 with a series of activities teaching binary mathematics.

Can teach the use of scientific calculators but not permitted on certification exams.


Objectives

Describe the purpose of an IP address and Subnet Mask and how they are used on the Internet.

Describe the types of IP Addresses available.

Describe the methods of obtaining an IP Address.

Describe the use of NAT on a home or small business network using an Integrated Router.


5.1.1 Purpose of the IP Address A logical address unique to a particular device IP Addresses assigned to host & end-user devices A subnet mask identifies the network. PACKET TRACER 5.1.1.2


5.1.2 IP Address Structure 32 Bits divided into four 8-bit sections called octets by periods Addresses are assigned using decimal, not binary numbers IP version 4

– Most common used– 4 trillion (4,294,967,296) possible addresses (232)– Example - 192.168.1.5


Binary Game!

ACTIVITY 5.1.2.3


5.1.2 IP Address Structure (Binary Game) 32 Bits divided into 4 8-bit sections called octets by periods Addresses are assigned using decimal, not binary numbers IP version 4

– Most common used– 4 trillion (4,294,967,296) possible addresses (232)


5.1.3 Parts of an IP Address IP Addressing is logical and heirarchical Example Address 192.168.100.39 (Class C)

– First section 192.168.100 is network portion– Second section 39 is host portion

Routers only need network address, not each host Less info in tables, faster routing Telephone system is also heirarchical, with country, area, and

exchange codes.


5.1.4 How IP Addresses and Subnet Masks Interact Every IP address has two parts, network and host

Subnet mask– Also 32-bit number– Compared with IP address bit to bit (ANDing)– 1s are network bits, 0s are host bits

Hosts compare address to its own before sending– Same mask - Local addresses have and sent locally– Different mask - Network addresses are sent to router

Most common masks: – 255.0.0.0 8 bit – 255.255.0.0 16 bit– 255.255.255.0 24 Bit


5.1.4 How IP Addresses and Subnet Masks Interact

Number of Hosts by Bits– If there are 8 host bits, there are 28 hosts possible, or 256 (0-255)– 16 bits - 216, or 65,536– 24 bits - 224, or 16,777,216

IP address that have all zeros in the host portion are network or subnetwork addresses, not available for hosts assignment

IP addresses with all 1s in the host portion are broadcast addresses, also not assigned


5.1.4 How IP Addresses and Subnet Masks Interact

AND Logic 1 and 1 = 1 1 and 0 = 0 0 and 1 = 0 0 and 0 = 0


5.2.1 IP Address Classes and Default Subnet Masks 5 Classes of IP address Default subnet masks

Network Size/Purpose

Large

Medium

Small

Multicast

Experimental


5.2.2 Private and Public IP Addresses

Public addresses are unique out on the Internet

Risk of using up all unique addresses

Introducing private addressing…


5.2.2 Private and Public IP Addresses RFC 1918 - Private Addressing

– Can be used within private network without going on Internet– Class A - Very Large - Over 16 million– Class B - Medium, about 65,000– Class C - Small, only 256 addresses, or 254 hosts– Unique class, 127.0.0.0 used for loopback addresses


5.2.2 Private and Public IP Addresses


5.2.3 Unicast, Broadcast, and Multicast Messages

Unicast – Most common– One destination

Broadcast– Contains all 1s in the host portion– All local hosts will receive and read packet– Used by ARP and DHCP– Example: 192.168.35.0 255.255.255.0 broadcast address is

192.168.35.255– Broadcast IP needs broadcast MAC address in Ethernet frame -

FF:FF:FF:FF:FF:FF (48 bits of 1) Multicast

– One source, many destinations– Address range is 224.0.0.0 to 239.255.255.255– Multicast IP needs matching Ethernet frame address

• Always begins with 01-00-5E



The IP packet has been encapsulated by the Framing information.


5.3.1 Static and Dynamic Address Assignment Methods of assigning an IP Address

– Static• Configured by host administrator• Used for servers, printers, and other

devices shared by users• Time consuming • List must be maintained• Can introduce errors

– Dynamic• Good where assignments change

often• DHCP (Dynamic Host Control

Protocol) used• Assigns other default information

–Subnet mask–Default gateway–DNS server, etc.

• Leased for period of time and returned to pool when not in use


5.3.2 DHCP Servers At the ISP (cable modem) At the ISP (internal to ISP) ISR in the home Dedicated DHCP server in a business


5.3.3 Configuring DHCP Newly configured hosts have no IP address, subnet mask, or gateway Needs to get this from a DHCP Server DHCP Process to get settings information:

– DHCP DISCOVER Packet• Broadcast

– IP: 255.255.255.255 – MAC: FF:FF:FF:FF:FF:FF

– DHCP server Replies with OFFER containing suggested IP address– Host sends REQUEST asking to use IP Address– Server replies with ACKNOWLEDGEMENT


DHCP Configuration on ISR


Animation 5.4.2.1 – Address Assignment


DHCP Configuration SOHO Networks usually use

an ISR for DHCP The basic DHCP Settings:

– Default network address for gateway on an ISR is normally a private Class C (192.168.1.1, 192.168.100.1)

– A pool of addresses– Lease time for address– Maximum number of hosts

• Can you exceed 20? Every host must have this Gateway

address configured– Either statically or dynamically – What does this mean? Describe

process– PACKET TRACER – 5.3.3.3


5.4.1 Network Boundaries and Gateways Routers for local networks provide gateway for communication to

other networks Each Interface on router is a separate network connection IP Addresses on interfaces identify networks connected ISP Side of the router

– ISPs use DHCP to give addresses to SOHO routers connecting to their network

– ISRs act as a DHCP client when connecting to ISP


Internet Connection Methods Direct Connection

– Single computer connected through a modem– ISP is assigned directly through modem to a single host

Connection through ISR – with Modem (WAN Device)– Many computers connected to ISR– ISR connected to ISP using connection through modem– ISP assigns address to ISR interface connected to modem– Hosts assigned addresses from ISR

Connection through Gateway Device – no Modem– Many computers connected to ISR– ISR connected to ISP with integrated modem port– ISP assigns address to ISR interface connected to modem– Hosts assigned addresses from ISR


Internet Connection Methods


5.4.3 Network Address Translation ISP provides public address for ISR to use externally ISR provides private addresses used on internal network NAT (Network Address Translation) is used to bridge the gap

and match the public and private addresses. Packets sent to the Internet have their IP addresses stripped

away and another, external address assigned. Reverse process is applied with incoming traffic. Animation 5.4.3.1


Using NAT with a Home or Small Business Network


Summary IP addresses are unique 32-bit addresses grouped into four 8-bit

bytes called octets. IP addresses use a two-part hierarchical structure of network

bits and host bits. IP addresses and subnet masks are used by routers to

determine the network location of hosts. IP addresses are grouped into classes according to the number

of bits used for designating the network, and further divided into public and private ranges.

Private IP addresses must be translated to public IP addresses in order to move through the Internet.

IP addresses can be assigned statically or dynamically.


Teacher Notes

URL for Subnetting guide - http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800a67f5.shtml

Students need to practice– Binary to Decimal Conversion– Decimal to Binary Conversion– Address Class Identification– Network and Host Identification– Default Subnet Masks

Subnet Workbook Guide

© 2007 cisco systems, inc. all rights reserved. 1 network addressing networking for home and small...

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