Network Addressing

1. Network Addressing Networking for Home and Small Businesses – Chapter 5 Darren Shaver – Modified Fall 2007

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.

3. IP Address and Subnet Mask • A logical address unique to a particular device • IP Addresses assigned to host & end-user devices

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 (232)

5. Purpose of an IP Address and Subnet Mask • 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.

6. 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: 255.0.0.0 8 bit 255.255.0.0 16 bit 255.255.255.0 24 Bit 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 Subnet Mask

7. Network ANDing Compare AND Logic • 1 and 1 = 1 • 1 and 0 = 0 • 0 and 1 = 0 • 0 and 0 = 0

8. 5 Classes of IP address Default subnet masks Network Size/ Purpose Large Medium Small Multicast Experimental Classes of IP Addresses

9. Private Addressing • Public addresses are unique out on the Internet • Risk of using up all unique addresses • RFC 1918 -PrivateAddressing • 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

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: 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

11. Unicast Frame • The IP packet has been encapsulated by the Framing information.

12. Broadcast Frame

13. Multicast Frame

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

15. DHCP Servers • Locations and methods of connection vary based on which network you’re associating with.

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: 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

17. DHCP Configuration • SOHO Networks usually use an ISR for DHCP • The basic DHCP Settings: • Default network addressfor 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…

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

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

20. Internet Connection Methods

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.

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.