IP ADDRESSING
1. IPv4 Every machine on the network has a unique identifying number, called an IP Address. It is a 32 bit addressing scheme to identify the devices on a network. To make it easier for us to remember, IP addresses are normally expressed in decimal format as a "dotted decimal number" (four decimal numbers separated by dots). A typical IP address looks like this -
216.27.61.137
But computers communicate address in binary form. Look at the same IP address in 32 bit binary format:-
11011000.00011011.00111101.10001001
The four numbers in an IP address are called octets, because they each have eight positions when viewed in binary form. If you add all the positions together, you get 32, which is why IP addresses are considered 32-bit numbers.
The octets are divided into two sections: Net and Host. The Net section always contains the first octet. It is used to identify the network that a computer belongs to. Host (sometimes referred to as Node) identifies the actual computer on the network. The Host section always contains the last octet. There are five IP classes plus certain special addresses.
2. Classes: There are 5 classes of IP addresses .These are as under:-
(a) Class A This class is for very large networks, such as a major international company might have. IP addresses with a first octet from 1 to 126 are part of this class. The other three octets are used to identify each host. This means that there are 126 Class A networks each with 16,777,214 (224 -2) possible hosts for a total of 2,147,483,648 (231) unique IP addresses. Class A networks account for half of the total available IP addresses. In Class A networks, the high order bit value (the very first binary number) in the first octet is always 0.
Loopback - The IP address 127.0.0.1 is used as the loopback address. This means that it is used by the host computer to send a message back to itself. It is commonly used for troubleshooting and network testing.
(b) Class B Class B is used for medium-sized networks. IP addresses with a first octet from 128 to 191 are part of this class. Class B addresses also include the second octet as part of the Net identifier. The other two octets are used to identify each host.
This means that there are 16,384 (214) Class B networks each with 65,534 (216 -2) possible hosts for a total of 1,073,741,824 (230) unique IP addresses. Class B networks make up a quarter of the total available IP addresses. Class B networks have a first bit value of 1 and a second bit value of 0 in the first octet.
(c) Class C Class C addresses are commonly used for small to mid-size Organizations. IP addresses with a first octet from 192 to 223 are part of this class. Class C addresses also include the second and third octets as part of the Net identifier. The last octet is used to identify each host. This means that there are 2,097,152 (221) Class C networks each with 254 (28 -2) possible hosts for a total of 536,870,912 (229) unique IP addresses. Class C networks make up an eighth of the total available IP addresses. Class C networks have a first bit value of 1, second bit value of 1 and a third bit value of 0 in the first octet.
(d) Class D Used for multicasts, Class D is slightly different from the first three classes. It has a first bit value of 1, second bit value of 1, third bit value of 1 and fourth bit value of 0. The other 28 bits are used to identify the group of computers the multicast message is intended for.
(e) Class E Class E is used for experimental purposes only. Like Class D, it is different from the first three classes. It has a first bit value of 1, second bit value of 1, third bit value of 1 and fourth bit value of 1. The other 28 bits are used to identify the group of computers the multicast message is intended for.
3. Features of IP Address Classes:
IP add class
|
IP address range
|
Example
|
No of NW supports
|
NO of hosts supports
|
Application
|
Class A
|
1.0.0.0 to 127.255.255.255 (127.0.0.1 reserved for loopback) | 124.12.20.6 | 126 | 16,777,216 |
Used in very large organizations with more than 65536 computers on a network and large ISPs.
|
Class B
|
128.0.0.0 to 191 | 168.154.12.3 | 16384 | 65,536 |
Used for more than 256 and fewer than 65536 computers on a network.
|
Class C
|
192.0.0.0 to 223.255.255.255 |
198.168.154.32 | 2097152 | 256 |
Most commonly used IP address classes in LANs.
|
Class D
|
224.0.0.0 to 239.255.255.255 | 225.255.251.124 | Not applicable | Not applicable |
Multicasts
|
Class E
|
240.0.0.0 to 255.255.255.255 | 242.103.26.125 | Not applicable | Not applicable |
Experimental purpose
|
4. IPv6 address
An Internet Protocol Version 6 address (IPv6 address) is a numerical label that is used to identify a network interface of a computer or other network node participating in an IPv6-enabled computer network.
IP addresses serve the purpose of uniquely identifying the individual network interface(s) of a host, locating it on the network, and thus permitting the routing of IP packets between hosts.
IPv6 is the successor to the Internet's first addressing infrastructure, Internet Protocol version 4 (IPv4). In contrast to IPv4, which defined an IP address as a 32-bit number, IPv6 addresses have a size of 128 bits. Therefore, IPv6 has a vastly enlarged address space compared to IPv4.
5. Difference between IPv4 and IPv6
IPv4
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IPv6
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a) ) It has a larger address space.
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a) IPv6 has a fixed length header
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b) IPv4 uses 4 bytes
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b) IPv6 uses 16 bytes.
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c) IPv4 can support up to 232 addresses.
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c) IPv6 support up to 2128 addresses
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d) IPv4 uses 4 bytes
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d) IPv6 uses 16 bytes.
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e) IPv4 is 32 bits IP address.
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e) Address extended to 128 bits.
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f) Enhanced Security and QoS Features
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6. Subnetting
1- A subnet is a segment of a network. Subnetting is a technique that allows a network administrator to divide one physical network into smaller logical networks and, thus, control the flow of traffic for security or efficiency reasons.
2- Dividing a network into several subnets can serve a number of purposes to reduce network traffic by decreasing the number of broadcasts to exceed the limitations in a local area network, for instance the maximum number of allowed hosts.
3- Subnets are created by using a so-called subnet mask to divide a single Class A, B, or C network number into smaller pieces. Subnets can again be subnetted into sub-subnets.
How does subnetting work?
An IP address consists of a network portion and a host portion. A subnet is created by borrowing bits from the part of the IP address which normally designates the Host And using them to designate one or smaller, secondary networks (subnets) within the original network. The network prefix and subnet number in combination are called the extended network prefix.
Subnet Mask A Subnet mask is a 32-bit number that masks an IP address, and divides the IP address into network address and Host Address. Subnet Mask is made by setting network bits to all "1"s and setting host bits to all "0"s. Within a given network, two Host Addresses are reserved for special purpose. The "0" address is assigned a network address and "255" is assigned to a broadcast address, and they cannot be assigned to a host. Examples of commonly used subnet masks for classed networks are 8-bits (Class A), 16-bits (Class B) and 24-bits (Class C), and classless (CIDR) networks are as follows:-
CIDR
|
/4
|
240,435,456
|
11110000 00000000 00000000 00000000
|
240.0.0.0
|
CIDR
|
/5
|
134,217,728
|
11111000 00000000 00000000 00000000
|
248.0.0.0
|
CIDR
|
/6
|
67,108,864
|
11111100 00000000 00000000 00000000
|
252.0.0.0
|
CIDR
|
/7
|
33,554,432
|
11111110 00000000 00000000 00000000
|
254.0.0.0
|
A
|
/8
|
16,777,216
|
11111111 00000000 00000000 00000000
|
255.0.0.0
|
CIDR
|
/9
|
8,388,608
|
11111111 10000000 00000000 00000000
|
255.128.0.0
|
CIDR
|
/10
|
4,194,304
|
11111111 11000000 00000000 00000000
|
255.192.0.0
|
CIDR
|
/11
|
2,097,152
|
11111111 11100000 00000000 00000000
|
255.224.0.0
|
CIDR
|
/12
|
1,048,576
|
11111111 11110000 00000000 00000000
|
255.240.0.0
|
CIDR
|
/13
|
524,288
|
11111111 11111000 00000000 00000000
|
255.248.0.0
|
CIDR
|
/14
|
262,144
|
11111111 11111100 00000000 00000000
|
255.252.0.0
|
CIDR
|
/15
|
131,072
|
11111111 11111110 00000000 00000000
|
255.254.0.0
|
CIDR
|
/16
|
65,534
|
11111111 11111111 00000000 00000000
|
255.255.0.0
|
CIDR
|
/17
|
32,768
|
11111111 11111111 10000000 00000000
|
255.255.128.0
|
CIDR
|
/18
|
16,384
|
11111111 11111111 11000000 00000000
|
255.255.192.0
|
CIDR
|
/19
|
8,192
|
11111111 11111111 11100000 00000000
|
255.255.224.0
|
CIDR
|
/20
|
4,096
|
11111111 11111111 11110000 00000000
|
255.255.240.0
|
CIDR
|
/21
|
2,048
|
11111111 11111111 11111000 00000000
|
255.255.248.0
|
CIDR
|
/22
|
1,024
|
11111111 11111111 11111100 00000000
|
255.255.252.0
|
CIDR
|
/23
|
512
|
11111111 11111111 11111110 00000000
|
255.255.254.0
|
CIDR
|
/24
|
256
|
11111111 11111111 11111111 00000000
|
255.255.255.0
|
CIDR
|
/25
|
128
|
11111111 11111111 11111111 10000000
|
255.255.255.128
|
CIDR
|
/26
|
64
|
11111111 11111111 11111111 11000000
|
255.255.255.192
|
CIDR
|
/27
|
32
|
11111111 11111111 11111111 11100000
|
255.255.255.224
|
CIDR
|
/28
|
16
|
11111111 11111111 11111111 11110000
|
255.255.255.240
|
CIDR
|
/29
|
8
|
11111111 11111111 11111111 11111000
|
255.255.255.248
|
CIDR
|
/30
|
4
|
11111111 11111111 11111111 11111100
|
255.255.255.252
|
Subnetting an IP network is to separate a big network into smaller multiple networks. Applying a subnet mask to an IP address separates network address from Host Address.
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COMPUTING KNOWLEDGE
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