Transcript Network Addressing

Network Addressing
Networking for Home and Small Businesses – Chapter 5
© 2007 Cisco Systems, Inc. All rights reserved.
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Teacher Notes
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It is highly recommended that the instructor begin
Chapter 5 with a series of activities teaching binary
mathematics.
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Can teach the use of scientific calculators but not
permitted on certification exams.
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Objectives
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Describe the purpose of an IP address and Subnet
Mask and how they are used on the Internet.
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Describe the types of IP Addresses available.
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Describe the methods of obtaining an IP Address.
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Describe the use of NAT on a home or small business
network using an Integrated Router.
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5.1.1 Purpose of the IP Address
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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
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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
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Binary Game!
 ACTIVITY 5.1.2.3
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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)
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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.
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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
– 255.255.0.0
– 255.255.255.0
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8 bit
16 bit
24 Bit
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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
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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
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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
 Experim
ental
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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…
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5.2.2 Private and Public IP Addresses
 RFC 1918 - Private Addressing
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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
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5.2.2 Private and Public IP Addresses
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5.2.3 Unicast, Broadcast, and Multicast Messages
 Unicast
– Most common
– One destination
 Broadcast
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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
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5.2.3 Unicast, Broadcast, and Multicast Messages
 The IP packet has been encapsulated by the Framing
information.
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5.2.3 Unicast, Broadcast, and Multicast Messages
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5.2.3 Unicast, Broadcast, and Multicast Messages
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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
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5.3.2 DHCP Servers
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At the ISP (cable modem)
At the ISP (internal to ISP)
ISR in the home
Dedicated DHCP server in a business
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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
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DHCP Configuration on ISR
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DHCP Configuration on ISR
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Animation 5.4.2.1 – Address Assignment
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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
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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
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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)
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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
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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
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Internet Connection Methods
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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
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Using NAT with a Home or Small Business Network
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Using NAT with a Home or Small Business Network
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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.
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Teacher Notes
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URL for Subnetting guide http://www.cisco.com/en/US/tech/tk365/technologies_
tech_note09186a00800a67f5.shtml
Students need to practice
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Binary to Decimal Conversion
Decimal to Binary Conversion
Address Class Identification
Network and Host Identification
Default Subnet Masks
Subnet Workbook Guide
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