IPv4 addressing
It is a numeric identifier assigned to each machine on an IP
network. It designates the specific location of a device on the network. An IP
address is a software address not a hardware address. IP address was designed
to allow hosts on one network to communicate with a host on a different
network.
IP Terminology
Bit – A bit is one digit, either a 1 or a 0.
Byte- a byte is 7 or 8 bits, depending on whether parity is
used.
Octet- an octet, made up of 8 bits, is just an ordinary
8-bit binary number.
Network address- this is the designation used in routing to
send packets to a remote network.
Broadcast address- the address used by application and host
to send information to allow nodes on a network is called the Broadcast
address.
The Hierarchical IP Address Scheme
An IP address consists o 32 bits of information. These bits
are divided into four sections, referred to as octets or byte, and each
containing 1 byte (8 bits). You can depict an IP address using one of three
methods: Dotted-decimal.
Network Address Range: Class A
The designers of the IP address scheme said
that the first bytes in a Class A network address must always be off or 0. This
means a Class A address must be between 0 and 127 in the first byte, inclusive.
· Network Address Range: Class B
Class B network is defined when the first
byte is configured from 128 to 191.
· Network Address Range : Class C
An IP address that starts at 192 and goes
to 223.
· Network Address Range: Classes D and E.
The addresses between 224 to 255 are reserved
for Class D and E networks. Class D (224-239) is used or multicast addresses
and Class E (240-255) for scientific purposes.
Network Addresses: Special Purpose
Some IP addresses are reserved
for special purpose, so network administrator can’t ever assign these addresses to
nodes.Address function Network 127.0.0.1 reserved for
loopback tests. Designates the local node and allows that node to send a test
packet to self without generating network traffic.
Node address of all 0s
interpreted to mean “network address” or any host on specified network.
Node address of all 1s
interpreted to mean “all nodes” on the specified network; for example,
128.2.255.255 means “all nodes” on network 128.2. (Class B address).
Enter IP address set all 0s used
by Cisco routers to designate the default route. Could also means “any network”.
Enter IP address set to all 1s
(same broadcast to all nodes on the current network; 255.255.255.255) sometimes
called an “all 1s broadcast” or limited broadcast.
Private IP address
The people who create the IP
addressing scheme also created what we call private IP addresses. These addresses
can be used on a private network, but they’re not routable through the
Internet.
This is designed for the purpose
of creating a measure of well-needed security, but it also conveniently save
valuable IP address space.
If every host on every network
had to have real routable IP addresses, we could have run out of IP addresses
to hand out years ago. But by using private IP addresses, ISPs, corporation,
and home users only need a relatively tiny group of bona fide IP addresses to
connect their networks to the Internet. This is economical because they can use
private IP addresses on their inside networks and get along just fine.
To accomplish this task, the ISPs
and the corporation- the end user, no matter who they are-need to use something
called Network Address Translation (NAT).
Address Class Reserved Address Space
Class A: 10 . 0 . 0 . 0 through
10 . 255 . 255 . 255
Class B: 172 . 16 . 0 . 0 through
172 . 31 . 255 . 255
Class C: 192 . 168 . 0 . 0 through 192 . 168 . 255 . 255
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