Network Addressing IP Addresses

IP Address Space The Structure of an IP Address – Binary Representation The only thing a network device understands, 32 binary bits: – – Hexadecimal Representation For nerdy humans, eight groups of four bits (nibbles) are converted to their equivalent hexadecimal value: – D8:7E:1F:AA – Dotted Decimal Notation For the rest of us, four groups of eight bits (octets) are converted to their equivalent decimal value. –

IP Address Space The 32 Bit IP Address – 232 (4,294,967,296) possible addresses are grouped into contiguous blocks – Historically, addresses were assigned by the Internet authorities in class-full licence units Ownership was transferred to the end user – Currently, addresses are assigned by an ISP from appropriately sized CIDR blocks (which we discuss later) – The ISP retains ownership

IP Address Space The 32 Bit IP Address: – Assigned to all hosts (interfaces) in a local network from a contiguous block of IP addresses – Provides each host with a Unique Logical Address Contains a network ID and unique host ID – The network ID must be unique within all interconnected networks – The Subnet Mask (which is the same for all interfaces in a network) determines where the division between the network ID and the host ID

IP Address Space Broadcast and Network addresses For any network the host portion cannot contain all zeros or all 1’s A host ID of all zeros is referred to as the Network address A host ID of all 1’s is referred to as the broadcast address Eg or or

IP Address Space Traditional Licence Classes – Class A – Class B – Class C – Class D – Class E

IP Classes Traditional Licence Class A NNN.HHH.HHH.HHH NNN = 000 to 127 decimal. nnnnnnnn = to binary. First Octet always begins with 0xxxxxxx 27 ( 128 ) available licences. 000 is not allowed / 127 is reserved / 010 is reserved 125 available licences (networks) ( 16,777,216-2 ) hosts per network 7

IP Classes Traditional Licence Class B NNN.NNN.HHH.HHH NNN.NNN = to decimal nnnnnnnn.nnnnnnnn = to binary. First Octet always begins with 10xxxxxx 26*28 or (214) or ( 64*256 ) = 16,384 available licences to are reserved ( 65, ) hosts per network. 8

IP Classes Traditional Licence Class C NNN.NNN.NNN.HHH NNN.NNN.NNN = to decimal. nnnnnnnn.nnnnnnnn.nnnnnnnn = to binary. First Octet always begins with 110xxxxx 25*28*28 or (221) or ( 32*256*256 ) = 2,097,152 available licences (networks) to are reserved ( ) hosts per network. 9

IP Classes Traditional Licence Class D Multicast Addresses MMM.HHH.HHH.HHH MMM = 224 to 239 decimal. mmmmmmmm = to binary. First Octet always begins with 1110xxxx. 10

IP Classes Traditional Licence Class E Experimental Addresses thru

IP Classes 12

IP Addressing IP Reserved and Private Addresses – Some octet numbers are reserved for special functions (eg. 10.x.x.x, 127.x.x.x, x.x x.x, and x.x) Loopback address – IP address reserved for communicating from a node to itself for testing purposes – Value of the loopback address is always

IP Address Exercise Are the following legal addresses for normal networks? Why or why not ?

Assigning IP Addresses Two ways to assign IP addresses – Dynamic Assigned by a Dynamic Host Configuration Protocol (DHCP) server Eliminates human error Allows for IP address reuse – Static Assigned by a network administrator Never change Must ensure that the settings are correct

Summary IP address is composed of 32 bits – Binary representation or dotted decimal Subnet mask is used to determine network ID and host ID Divided into classes – A, B, and C are routable Some addresses are reserved or are private Can be assigned dynamically or statically ARP maps IP addresses to MAC addresses