IP Address
An IP address is a unique set of number that is used to identify a device on a public or private network. IP stands for Internet Protocol; so IP Address is Internet Protocol address. It is the set of rules governing the format of data sent through a network. Therefore IP addresses are the unique recognition of all devices across the private as well as public network.
There are two types of addresses IPv6 and IPv4.
Let us discus about IPv4 addresses which are commonly known to us as 32 bit numbers presented in dotted decimal notation and it is separated by four octet place. Each octet place holds 8 bits or you can say 1 byte as because we know 8 bits is equals to 1 byte.
As we know computer can only understands 0s and 1s but we find easy to work with the decimal numbers. Therefore we provide the decimal numbers as the 32 bit IP address but the computer will convert those into 0s and 1s in those places.
Now let us understand; what is the minimum and maximum number that we can provide as the valid IP addresses.
Each octet has 8 bits and each of those bits can hold 1s that is (11111111) this is the maximum value for each octet place and it can holds all 0s that is (00000000) this is the minimum value for each octet place. If we convert the value of (11111111) into the decimal number then it will be 255 and if we convert the value of (00000000) into decimal number then the result will be 0. Here the minimum number that can be assigned as the octet value is 0 and the maximum octet value that can be assigned is 255 in each octet; that is the range between 0 to 255; so total 256 combinations.
The combination of 0s and 1s in each octet place can be of any type; 01001101 (decimal value results to 77), 00001111 (decimal value results to 15), 11001111 (decimal value results to 207), 11110000 (decimal value results to 240) and so on.
The 32 bit address contains two primary parts the first one is network number and the second is host number. All host devices within a single network share the same network addressing number but each and every host are recognized in the network by unique host addressing numbers.
Now let us discus about IPv6; it is 128 bit numbers used to identify and locate a network interface of a computer or a network node participating in a network. IPv6 came into existence in the purpose to take over and replace IPv4 protocol because in IPv4 addressing there can be the maximum of four billion IP addresses that will be assigned to the networking devices across the public network over the world. Therefore it is to be expected that the IPv4 will be exhausted soon and then IPv6 will come to use whose capacity of assigning IP addresses is just huge in compare to the IPv4. If we assign thousands of IP addresses per second then it will take billions of years to consume just its one percent of total addressing capacity.
IP Address Classes
There are five classes of IP address defined in TCP/ IP; Class A, B, C, D and E. Each class has a range of valid IP addresses and the value of the first octet determines which class this IP addresses is belonging to. The first three classes A, B and C can be used for host addresses. Class D addresses are used for multicast routing. Class E IP addresses are kept reserved for experimental and research purposes.
Class A 0.0.0.0 to 127.255.255.255
The first octet place holds the network number and the rest three octets hold the host numbers; that is why class A is defined as eight bit address.
Let us give an example of Class A IP address 10.23.45.22 / 8. This is eight bit address because the first octet holds the network value that is (10) and the rest three octets hold the host value that is (23.45.22).
Therefore we can have only 128 that is (28 - 1 = 27) possible networks in class A category of IP address because one bit out of 8 bits is kept reserved for identification of network category and 16,777,216 that is (224) hosts in each of the class A category network.
Class B 128.0.0.0 to 191.255.255.255
The first and second octet places hold the network number and the rest two octets hold the host numbers; that is why class B is defined as sixteen bit address.
Let us give an example of Class B IP address 130.120.140.24 / 16. This is sixteen bit address because the first and second octets hold the network value that is (130.120) and the rest two octets hold the host value that is (140.24).
Therefore we can have 16,384 that is (216 - 2 = 214) possible networks in class B category of IP address because two bits out of 16 bits is kept reserved for identification of network category and 65,536 that is (216) hosts in each of the class B category network.
Class C 192.0.0.0 to 223.255.255.255
The first three octet places hold the network number and the last octet holds the host numbers; that is why class C is defined as twenty-four bit address.
Let us give an example of Class C IP address 198.160.10.12 / 24. This is twenty four bit address because the first three octets hold the network value that is (198.160.10) and the last octet holds the host value that is (12).
Therefore we can have 2,097,152 that is (224 - 3 = 221) possible networks in class C category of IP address because three bits out of 24 bits is kept reserved for identification of network category and 254 that is (28 = 256 - 2 = 254) hosts in each of the class C category network because among the number of hosts first number that is 0 will be used as network ID and the last number that is 255 will be used as broadcast ID.
Class D 224.0.0.0 to 239.255.255.255
Class E 240.0.0.0 to 255.255.255.255
127.0. 0.0 / 8 belongs to class A category which is for use as the Internet host loopback address. A datagram sent by a higher level protocol to an address anywhere within this block should loop back inside the host. It is often use by the command localhost at our system browser to access our own resources of the device accessibility.
Subnetwork
The subnetwork or subnet is the most important component of an IP address. It is the logical subdivision of IP network addresses; so it is the practice of dividing a single network into two or more networks.
Subnet mask is a 32 bit number; that is created by setting host bits to all 0s and network bits to all 1s. In this way; the subnet mask separates the IP address into the host part and network part. The word mask has significant value because the subnet mask essentially uses its own 32 bit number to mask the IP address.
The default subnet of class A category network is 255.0.0.0.
There are four octets in this 32 bit number and the first octet is addressing to the network value which holds eight 1s (11111111) and the rest three octets is addressing to the host values by holding 0s (00000000.00000000.00000000).
The default subnet of class B category network is 255.255.0.0.
There are four octets in this 32 bit number and the first two octets is addressing to the network value which holds sixteen 1s (11111111.11111111) and the rest two octets is addressing to the host values by holding 0s (00000000.00000000).
The default subnet of class C category network is 255.255.255.0.
There are four octets in this 32 bit number and the first three octets is addressing to the network value which holds twenty four 1s (11111111.11111111.11111111) and the last octet is addressing to the host values by holding 0s (00000000).
Public IP Address
Public IP addresses are global addresses that are used on the Internet to identify a networking device. One device having a Public IP address can access another device across the internet having the unique public IP address. There are limited numbers of public IP address which are reserved for use and identify devices across the public network.
Private IP address
Private IP addresses are local or internal addresses that are assigned to the devices of an organization for the purpose of internal communication among different devices. The private IP addresses those are assigned to one organization can be same as the IP addresses assigned to another organization; but there will be no ambiguity to identify those devices uniquely because private IP addresses are only restricted its uses inside the organization.
Private IP addresses will never going to communicate with the public IP addresses and the private IP address of one organization cannot communicate with the private IP address of another organization.
Therefore on behalf of all private IP addresses of an organization a single public IP address can communicate across the public network that is over the internet through a specific process known as NAT (Network Address Translation) by using some devices that we will discuss in another lecture.
Network ID
Let us understand the network ID; it is the first value of host space that is identified as network ID; it is the portion of TCP/IP address which identifies the network for a given host and it is used by routers in order to find a network.
Broadcast ID
Broadcast ID is the last number after all host numbers that is used by nodes as the destination address when they want to send a broadcast requests for transmitting a message to all devices connected to a communications network then it is received by all hosts connected to network.
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