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IPv4 Subnetting

What is IPv4 Subnetting

IPv4 Subnetting, IP subnetting is a process of dividing a single IP network into multiple smaller subnetworks, or subnets. Subnetting allows network administrators to segment a large IP network into smaller, more manageable subnetworks, which can help improve network performance, security, and scalability.

Subnetting involves dividing the host portion of an IP address into multiple subnets by using a subnet mask. The subnet mask determines which portion of the IP address represents the network address and which portion represents the host address.

For example, if you have an IP address of 192.168.1.1 and a subnet mask of 255.255.255.0, this means that the first three octets (192.168.1) represent the network address, and the last octet (1) represents the host address. By changing the subnet mask, you can divide the network into smaller subnets.

Subnetting can be used to improve network security by isolating different departments or groups of users onto different subnets. It can also improve network performance by reducing broadcast traffic and improving the efficiency of routing.

Subnetting requires a good understanding of binary arithmetic and IP addressing, and there are many tools available to assist with the process, including subnet calculators and network planning software.

WHEN NEED IP SUBNETING

IP subnetting is needed when you want to divide a large IP network into smaller, more manageable subnetworks. Subnetting is typically done for the following reasons:

  1. Efficient use of IP addresses: When IP addresses are assigned to devices on a network, they must be unique. By using subnetting, you can divide a large IP address space into smaller subnets, which allows you to allocate IP addresses more efficiently.
  2. Improved network performance: Subnetting can improve network performance by reducing the amount of broadcast traffic on the network. Broadcast traffic is sent to all devices on a network, and it can slow down network performance. By dividing the network into smaller subnets, broadcast traffic is limited to devices within the same subnet.
  3. Improved network security: Subnetting can improve network security by isolating different departments or groups of users onto different subnets. This helps prevent unauthorized access to sensitive data or resources.
  4. Scalability: Subnetting allows you to divide a large network into smaller subnets that can be managed more easily. This can improve the scalability of the network, as it is easier to add new devices or subnets as the network grows.

Overall, subnetting is a useful tool for managing IP networks, and it is an essential skill for network administrators to master.

IP SUBNETTING RULES

There are several rules to keep in mind when subnetting an IP network:

  1. Every device on the network must have a unique IP address. This means that each subnet must have its own unique range of IP addresses.
  2. The subnet mask determines the size of each subnet. The subnet mask is a 32-bit number that indicates which part of an IP address represents the network address and which part represents the host address. The subnet mask is typically represented in dotted decimal notation, such as 255.255.255.0.
  3. The number of bits used for the network address and the number of bits used for the host address can vary depending on the size of the subnet. For example, a subnet with 256 IP addresses requires 8 bits for the host address, while a subnet with 64 IP addresses requires 6 bits for the host address.
  4. The first and last IP address in each subnet are reserved for the network address and broadcast address, respectively. This means that the usable IP addresses in a subnet are the ones between the first and last IP addresses.
  5. Subnets can be further divided into smaller subnets, known as sub-subnets. This is known as hierarchical subnetting.
  6. When designing subnets, it’s important to consider the needs of the network, such as the number of devices that will be connected, the amount of traffic on the network, and the level of security required.

Overall, subnetting is a flexible tool that can be adapted to meet the needs of any IP network. By following these rules, you can create subnets that are efficient, secure, and easy to manage.

SUBNET MASK EXTRACTION RULES

The subnet mask is a 32-bit number that is used to divide an IP address into two parts: the network address and the host address. The subnet mask determines which bits in the IP address are used for the network address and which bits are used for the host address.

The rules for extracting the subnet mask from an IP address depend on the class of the IP address:

For Class A IP addresses:

  • The first octet of the IP address represents the network address, and the remaining three octets represent the host address.
  • The subnet mask is 255.0.0.0 or /8, which means that the first 8 bits of the IP address are used for the network address, and the remaining 24 bits are used for the host address.

For Class B IP addresses:

  • The first two octets of the IP address represent the network address, and the remaining two octets represent the host address.
  • The subnet mask is 255.255.0.0 or /16, which means that the first 16 bits of the IP address are used for the network address, and the remaining 16 bits are used for the host address.

For Class C IP addresses:

  • The first three octets of the IP address represent the network address, and the last octet represents the host address.
  • The subnet mask is 255.255.255.0 or /24, which means that the first 24 bits of the IP address are used for the network address, and the remaining 8 bits are used for the host address.

For other IP address classes, such as Class D and Class E, subnet masks are not used in the same way as they are for Class A, B, and C addresses.

To summarize, the subnet mask can be extracted from an IP address based on the class of the address and the rules outlined above. It is important to understand subnet masks in order to effectively subnet IP networks.

HOW TO FIND NETWORK IP

To find the network IP address of a device, you need to know the IP address of the device and its subnet mask. The network IP address is the portion of the IP address that identifies the network, while the host IP address is the portion that identifies the specific device on the network.

Here are the steps to find the network IP address:

  1. Write down the IP address and subnet mask in binary form.
  2. Perform a bitwise AND operation between the IP address and the subnet mask. This will give you the network address in binary form.
  3. Convert the network address from binary to decimal form to get the network IP address.

Here is an example:

IP address: 192.168.1.100 Subnet mask: 255.255.255.0

  1. Convert the IP address and subnet mask to binary form:

IP address: 11000000.10101000.00000001.01100100 Subnet mask: 11111111.11111111.11111111.00000000

  1. Perform a bitwise AND operation between the IP address and subnet mask:

11000000.10101000.00000001.01100100 (IP address) 11111111.11111111.11111111.00000000 (Subnet mask)

11000000.10101000.00000001.00000000 (Network address)

  1. Convert the network address from binary to decimal form:

Network address: 192.168.1.0

Therefore, the network IP address for this device is 192.168.1.0

HOW TO FIND SUBNET MASK

To find the subnet mask of a device, you need to know the IP address of the device and the network ID or network IP address of the network it is connected to. The subnet mask determines which portion of the IP address is used for the network ID and which portion is used for the host ID.

Here are the steps to find the subnet mask:

  1. Write down the IP address of the device and the network ID in binary form.
  2. Compare the two addresses bit by bit, starting from the leftmost bit. When you encounter the first bit that is different, count the number of bits that are the same in both addresses up to that point. This gives you the length of the network ID in bits.
  3. Write down the subnet mask in binary form using the length of the network ID to set the bits that correspond to the network ID to 1 and the bits that correspond to the host ID to 0.
  4. Convert the subnet mask from binary to decimal form.

Here is an example:

IP address: 192.168.1.100 Network IP address: 192.168.1.0

  1. Convert the IP address and network IP address to binary form:

IP address: 11000000.10101000.00000001.01100100 Network IP address: 11000000.10101000.00000001.00000000

  1. Compare the two addresses bit by bit and count the number of matching bits:

IP address: 11000000.10101000.00000001.01100100 Network IP address: 11000000.10101000.00000001.00000000 — Number of matching bits: 24

  1. Write down the subnet mask in binary form using the length of the network ID:

11111111.11111111.11111111.00000000

  1. Convert the subnet mask from binary to decimal form:

Subnet mask: 255.255.255.0

Therefore, the subnet mask for this device is 255.255.255.0

HOW TO FIND FIRST IP

To find the first IP address in a subnet, you need to know the network IP address and the subnet mask. The first IP address in a subnet is the network ID plus one. The network ID is the portion of the IP address that identifies the network, as determined by the subnet mask.

Here are the steps to find the first IP address in a subnet:

  1. Write down the network IP address and subnet mask in binary form.
  2. Perform a bitwise AND operation between the network IP address and the subnet mask to find the network ID.
  3. Add one to the network ID to find the first IP address in the subnet.
  4. Convert the first IP address from binary to decimal form.

Here is an example:

Network IP address: 192.168.1.0 Subnet mask: 255.255.255.0

  1. Convert the network IP address and subnet mask to binary form:

Network IP address: 11000000.10101000.00000001.00000000 Subnet mask: 11111111.11111111.11111111.00000000

  1. Perform a bitwise AND operation between the network IP address and the subnet mask to find the network ID:

11000000.10101000.00000001.00000000 (Network IP address) 11111111.11111111.11111111.00000000 (Subnet mask)

11000000.10101000.00000001.00000000 (Network ID)

  1. Add one to the network ID to find the first IP address in the subnet:

11000000.10101000.00000001.00000000 (Network ID) +1

11000000.10101000.00000001.00000001 (First IP address)

  1. Convert the first IP address from binary to decimal form:

First IP address: 192.168.1.1

Therefore, the first IP address in this subnet is 192.168.1.1

HOW TO FIND LAST IP

To find the last IP address in a subnet, you need to know the network IP address and the subnet mask. The last IP address in a subnet is the broadcast address minus one. The broadcast address is the highest address in the subnet and is determined by setting all the bits in the host ID portion of the IP address to 1.

Here are the steps to find the last IP address in a subnet:

  1. Write down the network IP address and subnet mask in binary form.
  2. Perform a bitwise AND operation between the network IP address and the subnet mask to find the network ID.
  3. Invert the subnet mask to find the host ID mask.
  4. Perform a bitwise OR operation between the network ID and the host ID mask to find the broadcast address.
  5. Subtract one from the broadcast address to find the last IP address in the subnet.
  6. Convert the last IP address from binary to decimal form.

Here is an example:

Network IP address: 192.168.1.0 Subnet mask: 255.255.255.0

  1. Convert the network IP address and subnet mask to binary form:

Network IP address: 11000000.10101000.00000001.00000000 Subnet mask: 11111111.11111111.11111111.00000000

  1. Perform a bitwise AND operation between the network IP address and the subnet mask to find the network ID:

11000000.10101000.00000001.00000000 (Network IP address) 11111111.11111111.11111111.00000000 (Subnet mask)

11000000.10101000.00000001.00000000 (Network ID)

  1. Invert the subnet mask to find the host ID mask:

11111111.11111111.11111111.00000000 (Subnet mask) 00000000.00000000.00000000.11111111 (Host ID mask)

  1. Perform a bitwise OR operation between the network ID and the host ID mask to find the broadcast address:

11000000.10101000.00000001.00000000 (Network ID) 00000000.00000000.00000000.11111111 (Host ID mask)

11000000.10101000.00000001.11111111 (Broadcast address)

  1. Subtract one from the broadcast address to find the last IP address in the subnet:

11000000.10101000.00000001.11111111 (Broadcast address) -1

11000000.10101000.00000001.11111110 (Last IP address)

  1. Convert the last IP address from binary to decimal form:

Last IP address: 192.168.1.254

Therefore, the last IP address in this subnet is 192.168.1.254

HOW TO FIND BROADCAST IP

To find the broadcast IP address of a subnet, you need to know the network IP address and the subnet mask. The broadcast IP address is the highest address in the subnet and is determined by setting all the bits in the host ID portion of the IP address to 1.

Here are the steps to find the broadcast IP address:

  1. Write down the network IP address and subnet mask in binary form.
  2. Perform a bitwise AND operation between the network IP address and the subnet mask to find the network ID.
  3. Invert the subnet mask to find the host ID mask.
  4. Perform a bitwise OR operation between the network ID and the host ID mask to find the broadcast address.
  5. Convert the broadcast address from binary to decimal form.

Here is an example:

Network IP address: 192.168.1.0 Subnet mask: 255.255.255.0

  1. Convert the network IP address and subnet mask to binary form:

Network IP address: 11000000.10101000.00000001.00000000 Subnet mask: 11111111.11111111.11111111.00000000

  1. Perform a bitwise AND operation between the network IP address and the subnet mask to find the network ID:

11000000.10101000.00000001.00000000 (Network IP address) 11111111.11111111.11111111.00000000 (Subnet mask)

11000000.10101000.00000001.00000000 (Network ID)

  1. Invert the subnet mask to find the host ID mask:

11111111.11111111.11111111.00000000 (Subnet mask) 00000000.00000000.00000000.11111111 (Host ID mask)

  1. Perform a bitwise OR operation between the network ID and the host ID mask to find the broadcast address:

11000000.10101000.00000001.00000000 (Network ID) 00000000.00000000.00000000.11111111 (Host ID mask)

11000000.10101000.00000001.11111111 (Broadcast address)

  1. Convert the broadcast address from binary to decimal form:

Broadcast address: 192.168.1.255

Therefore, the broadcast IP address for this subnet is 192.168.1.255

HOW TO FIND TOTAL IP

To find the total number of IP addresses in a subnet, you need to know the subnet mask. The subnet mask determines the size of the subnet and how many IP addresses are available for use.

The formula for calculating the number of IP addresses in a subnet is:

2^(number of host bits) – 2

The “- 2” is because the first and last addresses in the subnet are reserved for the network address and the broadcast address, respectively.

Here’s an example:

Subnet mask: 255.255.255.0

In binary form, the subnet mask is:

11111111.11111111.11111111.00000000

The number of host bits is the number of zeros in the subnet mask, which is 8 in this case.

Using the formula above, we get:

2^8 – 2 = 256 – 2 = 254

Therefore, there are 254 available IP addresses in this subnet.

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