INTRODUCTION TO IP ADDRESS Ravi Chandra Gurung

IP ADDRESSES

WHAT IS AN IP ADDRESS? An IP address is a unique global address for a network interface An IP address: - is a 32 bit long identifier - encodes a network number (network prefix) and a host number

DOTTED DECIMAL NOTATION IP addresses are written in a so-called dotted decimal notation Each byte is identified by a decimal number in the range [0..255]: Example: st Byte = nd Byte = rd Byte = th Byte =

The network prefix identifies a network and the host number identifies a specific host (actually, interface on the network). How do we know how long the network prefix is?  The network prefix is implicitly defined (see class-based addressing)  The network prefix is indicated by a netmask. NETWORK PREFIX AND HOST NUMBER network prefix host number

Example: ellington.cs.virginia.edu Network id is: Host number is: Network mask is: or ffff0000 Prefix notation: /16  Network prefix is 16 bits long EXAMPLE

RESERVED ADDRESSES  Addresses beginning 127 are reserved for loopback and internal testing  xxx reserved for network address  xxx reserved for broadcast

9 IP ADDRESS CLASSES

10 IP ADDRESS CLASSES

11 IP ADDRESSES AS DECIMAL NUMBERS

12 HOSTS FOR CLASSES OF IP ADDRESSES Class A (24 bits for hosts) * = 16,777,214 maximum hosts Class B (16 bits for hosts) * = 65,534 maximum hosts Class C (8 bits for hosts) * = 254 maximum hosts * Subtracting the network and broadcast reserved address

13 IPV4 ADDRESS CLASSES Class D Addresses A Class D address begins with binary 1110 in the first octet. First octet range 224 to 239. Class D address can be used to represent a group of hosts called a host group, or multicast group. Class E Addresses First octet of an IP address begins with 1111 First octet range 240 to 255. Class E addresses are reserved for experimental purposes and should not be used for addressing hosts or multicast groups.

14 IP ADDRESSES AS DECIMAL NUMBERS

15 An IP address such as that has all binary 1s in the host bit positions is reserved for the broadcast address. An IP address such as that has all binary 0s in the host bit positions is reserved for the network address. NETWORK IDS AND BROADCAST ADDRESSES

16 PRIVATE ADDRESSES

DEFINITION Subnetwork, or subnet, is a logically visible, distinctly addressed part of a single Internet Protocol network. Subnetting is the division of a computer network into groups of computers that have a common, designated IP address routing prefix.

ADVANTAGES Allows a single shared network address to split it up into many smaller networks. Without subnets, organizations would require many network addresses  Limited number of Network addresses available Alleviates traffic  Smaller routing tables  Alleviates excessive packet collision and congestion Easier to manage and solve problems Better Security  Separating departments with highly sensitive material  Accounting and Administration