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Hey everyone,

I'm trying to get a solid grasp on subnetting and how it works with TCP/IP. I understand the basic concept of dividing a network into smaller subnetworks, but I'm struggling with the practical application, especially when dealing with different subnet masks and calculating usable host addresses.

Could someone explain the process of subnetting with a clear example? I've seen formulas like 2^n - 2 for host addresses, but I'm not sure how to correctly derive the network address, broadcast address, and the range of usable IPs for a given subnet mask.

For instance, if we have a network ID of 192.168.1.0 with a subnet mask of 255.255.255.0 (/24), how do we subnet this into smaller networks, say for different departments?

Any tips, resources, or step-by-step guides would be greatly appreciated!

Thanks in advance!

Hello NetworkGuru,

Subnetting can indeed be a bit tricky at first, but it's fundamental for efficient network management. Let's break down your example:

Example: 192.168.1.0 /24

Your base network is 192.168.1.0 with a /24 (255.255.255.0) subnet mask. This means the first 24 bits are for the network portion, and the remaining 8 bits are for host addresses.

• Total Addresses: 2⁸ = 256
• Usable Host Addresses: 2⁸ - 2 = 254
• Network Address: 192.168.1.0
• Broadcast Address: 192.168.1.255
• Usable IP Range: 192.168.1.1 to 192.168.1.254

Subnetting into Smaller Networks

To create smaller subnets, you borrow bits from the host portion and add them to the network portion. Let's say you want to create 4 equal subnets for different departments. You need 2 bits to represent 4 subnets (2² = 4).

So, we change the subnet mask from /24 to /26 (24 + 2 borrowed bits).

A /26 mask is 255.255.255.192.

Here's how the subnets would look:

Subnet 1 (Department A)

• Network Address: 192.168.1.0
• Subnet Mask: 255.255.255.192 (/26)
• Total Addresses: 2⁶ = 64 (8 host bits - 2 borrowed bits)
• Usable Host Addresses: 64 - 2 = 62
• Broadcast Address: 192.168.1.63
• Usable IP Range: 192.168.1.1 to 192.168.1.62

Subnet 2 (Department B)

• Network Address: 192.168.1.64
• Subnet Mask: 255.255.255.192 (/26)
• Broadcast Address: 192.168.1.127
• Usable IP Range: 192.168.1.65 to 192.168.1.126

Subnet 3 (Department C)

• Network Address: 192.168.1.128
• Subnet Mask: 255.255.255.192 (/26)
• Broadcast Address: 192.168.1.191
• Usable IP Range: 192.168.1.129 to 192.168.1.190

Subnet 4 (Department D)

• Network Address: 192.168.1.192
• Subnet Mask: 255.255.255.192 (/26)
• Broadcast Address: 192.168.1.255
• Usable IP Range: 192.168.1.193 to 192.168.1.254

The key is to remember that the increment in the network address part is determined by the 'magic number' of the last octet of the subnet mask, which is 64 in this case (256 - 192).

There are many great online subnet calculators that can help you visualize this process. I highly recommend using them to practice!