© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Constructing Network Addresses Classifying Network Addressing

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Outline Overview IP Addressing IP Address Structure IP Address Classes Reserved IP Addresses Public and Private IP Addresses IPv4 vs. IPv6 Summary Lab Exercise 5-2: Classifying Network Addressing

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Why IP Addresses? Uniquely identifies each device on an IP network so that data can be sent correctly to those locations. Real life analogies: –Address on a letter –Telephone number Every host (computer, networking device, peripheral) must have a unique address.

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Parts of the IP Address Each IP address consists of: Network ID –Identifies the network to which the host belongs –Assigned by registry authority and cannot be changed Host ID –Identifies the individual host –Assigned by organizations to individual devices

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v IP Address Format: Dotted Decimal Notation Remember binary-to-decimal and decimal-to-binary conversion.

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v IP Address Classes

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v IP Address Classes: The First Octet

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v IP Address Ranges *127 ( ) is a Class A address reserved for loopback testing and cannot be assigned to a network.

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Example Class B Network Address (Reserved) Total number of host addresses available = 2 h – 2 where h is the number of bits in the host field

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Example Class B Broadcast Address (Reserved) Total number of host addresses available = 2 h – 2 where h is the number of bits in the host field

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Public IP Addresses

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Private IP Addresses

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v IPv4 Address Allocation

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v IPv4 and IPv6

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Summary IP network addresses consist of two parts: the network ID and the host ID. IPv4 addresses have 32 bits that are divided into octets and are generally shown in dotted decimal form (for example, ). IPv4 addresses are divided primarily into A, B, and C classes. Other classes (D and E) exist, but they are reserved for special uses (multicasting and research). When written in a binary format, the first bit of a Class A address is always 0, the first 2 bits of a Class B address are always 10, and the first 3 bits of a Class C address are always 110.

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v Summary (Cont.) Certain IP addresses (network and broadcast) are reserved and cannot be assigned to individual network devices. Internet hosts require a unique, public IP address, but private hosts can have any valid private address that is unique within the private network. Address space as defined by IPv4 is limited and has been mostly exhausted. The more flexible IPv6 will replace IPv4 in the future. IPv6 offers 128 bits of addressing compared to the 32-bit addressing available in IPv4.

© 2005 Cisco Systems, Inc. All rights reserved.INTRO v