Transcript MCL-H0484 - Binus Repository

Matakuliah : H0484/Jaringan Komputer
Tahun
: 2007
IP Addressing
Pertemuan 18
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
• 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.
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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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Special IP Addresses
• 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
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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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Private IP Addresses
Rules:
• They cannot be referenced by hosts in another
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•
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•
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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
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
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Private IP Addresses
IANA reserves three ranges of IP addresses for "Private Internets":
• 10.0.0.0 - 10.255.255.255
A single Class A network
• 172.16.0.0 - 172.31.255.255
Sixteen continuous Class B Networks
• 192.168.0.0 - 192.168.255.255
256 contiguous Class C networks
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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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Subnetting
• 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
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Subnetting
• 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
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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 Notation
11111111.11111111.1111111.00000000
– Dotted Decimal Notation
255.255.255.0
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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.
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