Understanding IP Addresses.
An IP address is uniquely used to identify a device on an IP network. The address is made up of 32 binary bits, which can be divisible into a network portion and host portion with the help of a subnet mask. The 32 binary bits are broken into four octets (1 octet = 8 bits).
Each octet is converted to decimal and separated by a period (dot). For this reason, an IP address is said to be expressed in dotted decimal format (for example, 172.16.81.100). The value in each octet ranges from 0 to 255 decimal, or 00000000 – 11111111 binary.
Types of IP Addresses: There are two types of IP Addressing; IPv4 and IPv6.
This tutorial will only be based on IPv4.
IPv6 is the latest invention in IP addressing and is much more complex.
Subnetting IP Addresses
Subnetting allows you to create multiple logical networks that exist within a single Class A, B, or C network.
Each data link on a network must have a unique network ID, with every node on that link being a member of the same network. If you break a major network (Class A, B, or C) into smaller subnetworks, it allows you to create a network of interconnecting subnetworks. Each data link on this network would then have a unique network/subnetwork ID. Any device, or gateway, that connects n networks/subnetworks has n distinct IP addresses, one for each network/subnetwork that it interconnects.
There are so many reasons why we subnet:
IP Address Management: It helps in the preservation of address space in other not to waste addresses. Subnetting enables the efficient allocation of IP addresses by dividing a larger IP address space into smaller, more manageable subnets. This helps prevent IP address exhaustion and ensures that IP addresses are used effectively.
It is used for security. Subnetting is a method used to divide a larger network into smaller, more manageable sub-networks. This allows for better organization and control of network traffic. By separating devices into different subnets based on their functions or security needs, administrators can enforce access control and firewall rules to prevent unauthorized access and the spread of malware.
Subnetting also helps contain network issues, such as broadcast storms or malware outbreaks, by confining them to specific subnets. This prevents these problems from affecting the entire network and allows administrators to isolate and address them more efficiently.
Subnetting IP addresses helps control network traffic by preventing collisions of packets transmitted by other nodes (hosts) on the same segment. Subnetting also allows for efficient use of IP addresses by dividing a larger network into smaller subnetworks, each with its own unique subnet address. Additionally, subnetting can also help in optimizing network performance by reducing broadcast traffic and segmenting network traffic based on specific requirements or priorities.
Subnetting a Network Address
To subnet a network address, The subnet mask has to be extended, using some of the bits from the host ID portion of the address to create a subnetwork ID.
For example, given a Class C network of 192.17.5.0 which has a natural mask of 255.255.255.0, you can create subnets in this manner:
192.17.5.0 – 11000000.00010001.00000101.00000000
255.255.255.224 – 11111111.11111111.11111111.11100000
|sub|
By extending the mask to 255.255.255.224, you have borrowed three bits (indicated by “sub”) from the original host portion of the address and used them to create subnets. With these three bits, it is possible to create eight subnets. With the remaining five host ID bits, each subnet can have up to 32 host, addresses, 30 of which can be assigned to a device on the same segment.
These subnets have been created.
192.17.5.0 255.255.255.224 host address range 1 to 30
192.17.5.32 255.255.255.224 host address range 33 to 62
192.17.5.64 255.255.255.224 host address range 65 to 94
192.17.5.96 255.255.255.224 host address range 97 to 126
192.17.5.128 255.255.255.224 host address range 129 to 158
192.17.5.160 255.255.255.224 host address range 161 to 190
192.17.5.192 255.255.255.224 host address range 193 to 222
192.17.5.224 255.255.255.224 host address range 225 to 254
Another example:-
Given a class C network address of 192.168.1.0, as a network administrator, you need to utilize this network address across multiple small groups within the organization. You can do this by subnetting this network with a subnet address.
All you have to do is, try to create 14 subnets of 14 nodes (hosts) each. This will limit us to 196 nodes (hosts) on the network instead of the 254 we would have without subnetting. To accomplish this we begin with the default network mask for class C
255.255.255.0 (11111111.11111111.11111111.00000000) binary
255.255.255.240 (11111111.11111111.11111111.11110000) binary
1 1 1 1 1 1 1 1
128 64 32 16 8 4 2 1 (128+64+32+16+8+4+2+1=255)
Look at this closely, you will always come across it during subnetting
128+64 =192
128+64+32 =224
128+64+32+16=240
128+64+32+16+8=248
128+64+32+16+8+4=252 and so on!
So to give us 16 possible network numbers, 2 of which cannot be used:-
192.168.1.0 (Reserved)
Network address hosts address, broadcast address
192.168.1.16 192.168.1.17 – 30 192.168.1.31
192.168.1.32 192.168.1.33 – 46 192.168.1.47
192.168.1.48 192.168.1.49 – 62 192.168.1.63
192.168.1.64 192.168.1.65 – 78 192.168.179
192.168.1.80 (keep adding 16 till you get to 224)
That will give you up to 14 networks shared among 14 hosts (nodes).
In Summary
Subnetting IP Address is important to carefully plan and allocate the available address space to optimize network performance and efficiency. This involves dividing the IP address range into smaller subnets, each with its own unique network address and range of host addresses. By subnetting effectively, you can better manage your network traffic, improve security, and streamline network administration tasks.
