Network Address

Content
1. Network Address
2. Types of network address
● Physical address
● Logical address
i. Different Classes of Logical address
3. Type of Logical Address
● Public IP address
● Private IP address
4. Subnet Mask
5. Network Layer Protocol
● ARP Mapping Logical to Physical address
● RARP Mapping Physical to logical address
6. Calculation of subnet mask, broadcast ID , network ID and Other IP’s.

Network Address
A network address is the unique code or number which is given to each node
or device in the network.
Each device has its own unique address and it make easy for the users to
communicate within a network
Examples of network addresses are:
● A telephone no in the public switched telephone (PSTN) network
● An IP address in the Internet
● MAC address in an Ethernet network etc

Types of Network Address

Physical address
● The MAC (Media Access Control) address is a physical address.
● MAC address is 48 bits in length.
● This unique code is given by manufacturer which is encoded in NIC card.
● It is associated with Data Link Layer of OSI model.
● It is also known as Hardware address.
● The format of address is Hexadecimal.
● Example of MAC address 00-23-4E-47-21-01
● MAC address are used by many different Layer 2 devices some are Ethernet, Token Ring and Fiber Channel.

Logical Address
● The IP (Internet Protocol) address is a Logical Address.
● IP address is 32 bits in length.
● IP address are assigned by ISP (Internet service provider) to the device.
● It is associated with network layer of OSI model.
● It is also known as virtual address.
● Format of address is Decimal ranges from 0 to 255.
● Example of IP address 209.161.122.70.
● The IP address is used to identify the different computers and websites on the internet or intranet.

Automatically Assigned IP address
There are IP addresses that are automatically assigned (dynamic allocation)
when you set up a home network.
192.168.1.0 0 is automatically assigned network address.
192.168.1.255 255 is commonly used as Broadcast address.
192.168.1.1 1 is commonly used as Gateway Address.

Different Classes of Logical address
Ranges 127.x.x.x are reserved for the loopback testing , for example, 127.0.0.1 is
the loopback address.
All IP addresses uniquely identifies a device in the network.
Some IP Addresses cannot used in the network because they are used for
some special purposes.
All zero’s in Host ID represent the Network Address.
All One’s in Host ID represent the Broadcast address.

Type Of Logical Address
Logical Network Is divided into two parts:
1. Private IP address
2. Public IP address

Public IP Address
The public IP address is assigned to the computer by the Internet Service
Provider when it is connected to the Internet Service.
A public IP address can be assigned as static or dynamic.
A static public IP address remain unchanged and is used for hosting web
pages or services on the Internet.
A dynamic public IP address is chosen from a pool of available addresses and
it changes each time as a device connects to the Internet.

Private IP Address
An Private IP address is a IP number which falls within one of the IP address
ranges reserved for private networks such as a Local Area Network (LAN).
The Internet Assigned Numbers Authority (IANA) has reserved the following 3
blocks of the IP address as private networks :
Class A 10.0.0.0 – 10.255.255.255
Class B 172.16.0.0 – 172.31.255.255
Class C 192.168.0.0 – 192.168.255.255

Private IP Address
For example,if a network A consists of 20 computers, each of them can be
given an IP starting from 192.168.1.1 to 192.168.1.20. Thus the assigned IP
address must range as mentioned above for efficient communication
between a computers of Private Network.
Devices with private IP addresses cannot connect directly to the Internet.
Computers outside the local network cannot connect directly to a device
having private IP address or device within Private network.

If the private network is connected to the Internet then each computer will
have a private IP address as well as a public IP address.
Public IP Address is assigned by ISP (Internet Service Provider) to connect a
device to the internet.
Private IP is used for communication within the network and the public IP is
used for communication over the Internet.

Subnet Mask
A Subnet mask is a 32-bit number that divides the IP address into network
address and host address.
It is used to determine to what subnet an IP address belongs to.
Subnet Mask is made by setting network bits to all “1”s and host bits to all “0”s.
Subnet Mask Of different classes are:
Class A 255.0.0.0/8
Class B 255.255.0.0/16
Class C 255.255.255.0/24

Network Layer Protocol

There are two type of network Protocol
1. ARP Address Resolution Protocol
2. RARP Reverse Address Resolution Protocol
These Protocols are used for mapping physical address into logical
address or vice-versa.

1. Address Resolution Protocol (ARP)
The address resolution protocol (ARP) is a protocol used in network to map
(Logical Address) IP network addresses to the (Physical Address) hardware
addresses used by a data link protocol.
In IPv4 ,an IP address is 32 bits long whereas in an Ethernet LAN, however,
addresses of an attached device is 48 bits long known as MAC address. A table
called the ARP cache, is used to maintain a relation between each MAC
address and its corresponding IP address. ARP provides the protocol rules for
making this relation and providing address conversion in both directions.

For example: There are 2 computers in network wants to communicate.
Computer A wants to send packet to computer B but Computer A only knows
the IP address of Computer B but don’t know its MAC address. So, to get MAC
address. First of all Computer A checks the ARP cache table to find
corresponding MAC address to IP address of Computer B.if not found
then,Computer A broadcast a ARP request Message in the network.Each
Computer in Network check the ARP request and match the given IP address.
After matching IP address Computer B sends a unicast message to Computer
A with its IP address and MAC address. This MAC address get stored in ARP
cache for future use. Now Computer A can send packets to Computer B.

2. Reverse Address Resolution Protocol (RARP)
The Reverse Address Resolution Protocol (RARP) is a computer networking
protocol used by a client computer to request its Internet Protocol(IPv4)
address from a computer network, using MAC address or hardware address.
It is a protocol by which a device in a LAN can request to have its IP address
from a gateway server’s ARP cache.
A network administrator creates a table in a LAN gateway router that maps
the physical machine MAC address addresses to corresponding IP addresses.

For example: When a new machine is set up in the network, it send RARP
requests on the router in the network to be sent its IP address which
corresponds to its MAC address.. Assuming that an entry has been set up in the
router table, the RARP server return the IP address to the machine and store it for future use.

Calculation
How to calculate the subnet mask, broadcast IP address, network IP address
and other related IP address of given IP address.
1. 192.168.1.5
Here 192 in first octet represent the class of an IP address. Thus this IP address
belongs to Class C.
Then calculate the subnet mask, as this IP belongs to class C so the subnet
mask of class C be : 255.255.255.0 or /24
Thus, 192.168.1. 5
Network bits Host bits

We know Network IP address contain all zeros in host bits. So, to find n/w IP
make all host bits equal to 0.
11000000.10101000.00000001.00000000 = 192.168.1.0
Thus Network IP address is 192.168.1.0
We know Broadcast IP address contain all one’s in host bits. So, to find
Broadcast IP make all host bits equal to 1.
11000000.10101000.00000001.11111111= 192.168.1.255
Thus Broadcast IP address is 192.168.1.255

So IP address ranges from 192.168.1.0 to 192.168.1.255
192.168.1.0 – N/w address
192.168.1.1
……
…….
192.168.1.254
192.168.1.255 – Broadcast address
Total IP address =256
1 Network IP and 1 Broadcast IP both are invalid IP addresses.
So, there are total 254 IP addresses which are valid and can be used in
network.

We can also calculate as
No. of Host bits =8
2^8= 256 -total IP addresses
2^8-2 = 254 – valid IP address

Calculate the subnet mask, broadcast IP address, network IP address and
other related IP address of given IP address:
2. 170.168.60.1
Here 170 in first octet represent the class of an IP address. Thus this IP address
belongs to Class B.
Then calculate the subnet mask, as this IP belongs to class B so the subnet
mask of class C be : 255.255.0.0 or /16
Thus, 170.168. 60.1
Network bits Host bits

We know Network IP address contain all zeros in host bits. So, to find n/w IP
make all host bits equal to 0.
10101010.10101000.00000000.00000000 = 170.168.0.0
Thus Network IP address is 170.168.0.0
We know Broadcast IP address contain all one’s in host bits. So, to find
Broadcast IP make all host bits equal to 1.
10101010.10101000.11111111.11111111= 170.168.255.255
Thus Broadcast IP address is 170.168.255.255

So IP address ranges from 170.168.0.0 to 170.168.255.255
170.168.0.0 – N/w address
……..
170.168.0.255
170.168.1.0
…….
170.168.1.255
170.168.2.0
…….
170.168.2.255
……
170.168.255.254
170.168.255.255 – Broadcast address

Total IP address =65536 (256X256)
1 Network IP and 1 Broadcast IP both are invalid IP addresses.
So, there are total 65534 IP addresses which are valid and can be used in
network.
Or We can also calculate as
No. of Host bits =16
2^16= 65536 -total IP addresses
2^16-2 = 65534 – valid IP address

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