IP Address 32 bits in length Contains two parts –Network number –Host number Binary in nature Expressed in a format that can be read by the human eye

IP Address Sections Broken into 4 sections of 8 bits called octets Each octet is converted to decimal format and is separated by dots | | | | | |

Octets Minimum octet value is 0 – all zeros Maximum octet value is 255 – all ones

Address Allocation Addresses are allocated by a central authority, the American Registry of Internetwork Numbers (ARIN) See for more informationwww.arin.net

Early IP Addresses Early IP addresses did not use classes because there weren’t very many networks Now a class system is necessary to increase the number of available IP addresses

IP Address Classes 8 Bits Class ANetworkHost Class BNetwork Host Class CNetwork Host Class DMulticast Class EResearch

Analysis of Class System Class A networks have only 8 network bits and 24 host field bits Therefore, there are few Class A networks There are more Class B networks and even more yet Class C networks each with fewer hosts Class system allows addresses to be assigned based on the size of the network There are many more small networks than there are large networks

Address Classification Bits: Class A:0NNNNNNNHost Range(1–126) Bits: Class B:10NNNNNNNetworkHost Range(128–191) Bits: Class C110NNNNNNetwork Host Range(192–223)

Class Ranges Class AClass BClass C Starts with: Range: to to to Networks:127 (1-126) 127 is reserved 16,3842,097,152 Hosts:16,777,216 – 265,536 – 2256 – 2

Class D – Multicast Addresses Bits: Class D:1110MMMMMulticast Grp Range(224–239) Includes the following range of network numbers: to

Class E – Research Addresses Bits: Class E:11110RRRResearch Grp Range(240–247) Includes the following range of network numbers: to

Reserved Addresses RFC 1918 defines the following as reserved addresses: through through through

Host Addresses Router E E RoutingTable NetworkInterface E E1

Host Address Conventions Host address of 0 means this network or wire address, i.e., Router uses network address to identify subnet Routing table contains entries for each network All 1s is a broadcast address. Number of addresses in network is 2 N – 2

Default Subnet Masks ClassFormatDefault Subnet Mask Anetwork.node.node.node Bnetwork.network.node.node Cnetwork.network.network.node

Subnet Example Router E E RoutingTable NetworkInterface E E1

Subnet Mask Example network host IP Address network host Default Mask written as:/16 network subnethost Subnet Mask written as:/24

Subnet Mask Numbering 1 for network bits 1 for subnet bits 0 for host bits

Methods of Representation Dotted Decimal – Bit Count – /16 Hexadecimal – xFFFF0000

Possible Subnet Mask Values = = = = = = = =255

Calculating Network Number – No Subnet Bits /16 network host Network Number

Calculating Subnet Number – 8 Subnet Bits /24 network host Subnet Number

Calculating Subnet Number – 10 Subnet Bits /26 network subnethost Subnet Number

Class B Broadcasts From Local to Subnet 1 – Specific to Subnet 3 – To All Subnets –

Defining Class B Subnet – / host mask subnet broadcast first last

Defining Class B Subnet – / host mask subnet broadcast first last

Possible Class B Combinations bitssubnet masksubnetshosts

Network Design Class C Network with address Supports at least 20 subnets – 5 bits Each Subnet has at least 5 hosts – 3 bits

Class C Network Specifications – /29 network subnethost host mask subnet broadcast first last

Possible Class C Combinations bitssubnet masksubnetshosts