A subnet mask is a 32-bit number that segments an IP address into two parts: the network part and the host part. It’s used to determine which portion of an IP address identifies the network and which part identifies individual devices within that network. Subnet masks are primarily associated with IPv4 addresses.
In a subnet mask, the bits that are set to 1 represent the network portion, and the bits set to 0 represent the host portion. By applying a subnet mask to an IP address using a process called “bitwise AND,” you can determine the network address for a given IP address.
Here’s a simple example:
Suppose you have the IP address 192.168.1.10 with a subnet mask of 255.255.255.0.
- IP Address: 192.168.1.10
- Subnet Mask: 255.255.255.0
When you perform a bitwise AND operation between the IP address and the subnet mask:
IP Address: 11000000.10101000.00000001.00001010 (in binary)
Subnet Mask: 11111111.11111111.11111111.00000000 (in binary)
Result: 11000000.10101000.00000001.00000000 (in binary)The result of this operation gives you the network address, which is 192.168.1.0 in this case. The host portion (the last 8 bits) is all zeros, indicating that it can be used to address individual devices within the 192.168.1.0 network.
Subnet masks allow for the efficient allocation of IP addresses within networks. They help divide larger IP address ranges into smaller, manageable subnetworks, which can improve network organization and security. Subnetting is a fundamental concept in IP networking.