IP AddressingPertemuan 18

Matakuliah : H0484/Jaringan KomputerTahun : 2007

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Learning Outcomes

Pada akhir pertemuan ini, diharapkan mahasiswa

akan mampu :

• Menjelaskan IP Addressing

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Outline Materi

• Classful Addressing• Special Addresses• Subnet mask

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• IP Address– A logical address used in TCP/IP networking for

identifying a host in the network• IP Address Characteristics

– An IP address is 32 bits in size, unique, grouped into four 8-bit octets

– Octets are separated by decimal points• Network Administrator

– IP addresses are assigned by a network administrator according to an organization’s valid IP address range.

• ICANN (Internet Corporation for Assigned Names & Numbers) – Central authority on Internet addresses and names. – A group of IP addresses must be obtained via an ISP.

IP Address

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IPv4 Address Formats

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Classful Addresses

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Network Addresses

•In classful addressing, the network address is the one that is assigned to the organization

•The network address defines the network to the rest of the Internet.

•Given the network address, we can find the class of the address, the block, and the range of the addresses in the block

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• Some IP address numbers are reserved for special functions.

• IP address whose numeric value is the highest value in the network (host bits all equal to one) is a broadcast address.

• IP addresses with first octet of 127 such as 127.0.0.1 is a loopback IP used to test local workstation communication

• IP addresses ending in “1” are typically reserved for gateway

Special IP Addresses

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Private Addresses

• A number of blocks in each class are assigned for private use. They are not recognized globally

• Several techniques exist to hide internal network IP addresses from outside view

• Within the Class A, B, and C IP address ranges, the IETF has reserved private IP addresses or address ranges

• Any organization can use these addresses provide they adhere to the rules

• All connectivity to an Internet host must be provided by a Network Address Translator

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Rules:

•They cannot be referenced by hosts in another organization

•They cannot be defined to any external router

•Organization with private addresses cannot externally advertise those IP

•Addresses and cannot forward IP datagrams containing those addresses to external routers

•External routers will quietly discard all routing information regarding these addresses

Private IP Addresses

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Private IP addresses relax the rule that IP addresses are globally unique

•This IP conservation technique reserves part of the IP address space for use exclusively within an organization

•The organization does not require connectivity to the Internet

Private IP Addresses

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IANA reserves three ranges of IP addresses for "Private Internets":

•10.0.0.0 - 10.255.255.255A single Class A network

•172.16.0.0 - 172.31.255.255Sixteen continuous Class B Networks

•192.168.0.0 - 192.168.255.255256 contiguous Class C networks

Private IP Addresses

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Subnetting

Subnetting Allows the use one class of addresses for several

network segments

A subnetted address is comprised of three parts Network address Subnet address Host address

Subnet address uses part of the host address for subnet address assignment

Efficient use of IP addresses

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• A subnet mask is a special bit pattern that blocks off the network portion of an IP address with an all-ones pattern

• The entire network address, including the network prefix and the subnetting bits, is called the extended network prefix

• This activity of stealing bits from the host portion of further subdivide the network portion of an address is called subnetting a network address, or subnetting

Subnetting

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• A subnet mask that is larger than the default mask for the address in use divides a single network IP address into multiple subnetworks

• The network prefix identifies the number of bits in the IP address, counting from the left that represents the actual network address itself, and the additional bits of subnetting represent the bits that were borrowed from the host portion of that IP address to extend the network portion

• When a computer on one subnet wishes to communicate with a computer on another subnet, traffic must be forwarded from the sender to a nearby IP gateway to send the message on its way from one subnet to another

Subnetting

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Subnetting

Subnet mask composed of four octets and can be expressed in either binary or dotted decimal notation

– Octet of all 1’s • Represents part of the extended network

prefix that uses that subnet mask.– Octet of all 0’s

• Represents corresponding octets that are assumed to represent host information.

– Binary Notation11111111.11111111.1111111.00000000

– Dotted Decimal Notation255.255.255.0

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Default mask and subnet mask

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Subnetting

First 2 octets represent part of extended network prefix.

3rd octet represents subnet. 4th octet represents

host/machine/device.

Router needed to interpret addresses. IP ending in “1” always reserved for gateways address.