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.
Key terms in plain language
Open a term for a concise explanation of language used on this page.
Fiber Internet
Internet delivered through strands of glass using light. Fiber commonly supports high capacity, low latency, and strong upload performance, but availability must be confirmed for the exact address.
Cybersecurity
The practices and controls used to protect identities, devices, networks, applications, and data from unauthorized access, disruption, or manipulation.
Zero Trust
A security model that does not automatically trust a user or device because of its location. Access is continuously verified and limited to what is necessary.
SASE
Secure Access Service Edge combines networking and security capabilities in a cloud-delivered architecture so users and locations can receive consistent policy wherever they connect.
Identity and Access Management (IAM)
The systems and policies that determine who a user is, what resources they may access, and how that access is authenticated and reviewed.
Multi-Factor Authentication (MFA)
A login control requiring more than one form of verification, such as a password plus an authenticator app, security key, or biometric factor.