© 2007 Cisco Systems, Inc. All rights reserved. 1 Network Addressing Networking for Home and Small Businesses – Chapter 5 Darren Shaver – Modified Fall 2007

Cisco Discovery Home & Small Business Chapter 5 2 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.

Cisco Discovery Home & Small Business Chapter 5 3 IP Address and Subnet Mask  A logical address unique to a particular device  IP Addresses assigned to host & end-user devices

Cisco Discovery Home & Small Business Chapter 5 4 Structure of an IP Address  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 (2 32 )

Cisco Discovery Home & Small Business Chapter 5 5 Purpose of an IP Address and Subnet Mask  IP Addressing is logical and heirarchical  Example Address (Class C) –First section 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.

Cisco Discovery Home & Small Business Chapter 5 6 Subnet Mask  Every IP address has two parts, network and host  How does the host, router, or other device know which?  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: – bit – bit – Bit  Number of Hosts by Bits –If there are 8 host bits, there are 2 8 hosts possible, or 256 (0-255) –16 bits , or 65,536 –24 bits , 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

Cisco Discovery Home & Small Business Chapter 5 7 Network ANDing Compare AND Logic  1 and 1 = 1  1 and 0 = 0  0 and 1 = 0  0 and 0 = 0

Cisco Discovery Home & Small Business Chapter 5 8 Classes of IP Addresses  5 Classes of IP address Default subnet masks Network Size/ Purpose  Large  Medium  Small  Multicast  Experim ental

Cisco Discovery Home & Small Business Chapter 5 9 Private Addressing  Public addresses are unique out on the Internet  Risk of using up all unique addresses  RFC 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, used for loopback addresses

Cisco Discovery Home & Small Business Chapter 5 10 Types of IP Packets and Frames  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: broadcast address is –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 to –Multicast IP needs matching Ethernet frame address Always begins with E

Cisco Discovery Home & Small Business Chapter 5 11 Unicast Frame  The IP packet has been encapsulated by the Framing information.

Cisco Discovery Home & Small Business Chapter 5 12 Broadcast Frame

Cisco Discovery Home & Small Business Chapter 5 13 Multicast Frame

Cisco Discovery Home & Small Business Chapter 5 14 Obtaining an IP Address  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

Cisco Discovery Home & Small Business Chapter 5 15 DHCP Servers  Locations and methods of connection vary based on which network you’re associating with.

Cisco Discovery Home & Small Business Chapter 5 16 DHCP Configuration on ISR  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: –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

Cisco Discovery Home & Small Business Chapter 5 17 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 ( , ) –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…

Cisco Discovery Home & Small Business Chapter 5 18 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

Cisco Discovery Home & Small Business Chapter 5 19 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

Cisco Discovery Home & Small Business Chapter 5 20 Internet Connection Methods

Cisco Discovery Home & Small Business Chapter 5 21 Using NAT with a Home or Small Business Network  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.

Cisco Discovery Home & Small Business Chapter 5 22 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.

Cisco Discovery Home & Small Business Chapter 5 23