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255.255.255.0 Subnet Mask for IP Networks

Master the secrets of the subnet mask 255.255.255.0

By Bradley Mitchell Bradley Mitchell Writer Massachusetts Institute of Technology University of Illinois An MIT graduate who brings years of technical experience to articles on SEO, computers, and wireless networking. lifewire's editorial guidelines Updated on November 17, 2020 Reviewed by Jessica Kormos Reviewed by Jessica Kormos Saint Mary-of-the-Woods College Jessica Kormos is a writer and editor with 15 years' experience writing articles, copy, and UX content for Tecca.com, Rosenfeld Media, and many others. lifewire's editorial guidelines Tweet Share Email Tweet Share Email Home Networking ISP The Wireless Connection Routers & Firewalls Network Hubs Broadband Ethernet Installing & Upgrading Wi-Fi & Wireless The subnet mask 255.255.255.0 address is the most common subnet mask used on computers connected to Internet Protocol (IPv4) networks. Besides its use on home network routers, you might also encounter this mask on network professional certification exams such as the CCNA.

255 255 255 0 and Subnetting

Lifewire / Joshua Seong Subnets act as virtual fences, splitting a block of IP addresses into smaller units. This practice relieves network congestion and allows for granular access across subnets. A subnet mask identifies individual subnets. Traditional subnets worked with classful networks that partitioned the IP addresses into one of five classes (Class A/B/C/D/E) according to the value of the IP address number. The subnet mask 255.255.255.0 converts to a 32-bit binary value: 11111111 11111111 11111111 00000000 The 0 digits of this mask span the IP range of the subnet—8 bits or up to 256 addresses in this case. A larger number of smaller-sized subnetworks can also be defined by modifying the mask as shown in the table below. Classful Subnets Based on the 255.255.255 Mask Prefix Mask Subnetworks Nodes/Subnet 255.255.255.0 1 254 255.255.255.128 2 126 255.255.255.192 4 62 255.255.255.224 8 30 255.255.255.240 16 14 255.255.255.248 32 6 255.255.255.252 64 2 An incorrectly configured subnet mask (also called netmask) could be the reason why you can't connect to the internet.

Subnets and CIDR

In the traditional classful scheme, many unused IP addresses were wasted because internet service providers and large corporations reserved address blocks that could not be shared. Much of the internet subsequently converted to classless IP networking to support flexible allocation policies and cope with the surge in demand for IPv4 internet addresses in the 1990s. Classless networks convert the traditional subnet representation to a shorthand notation based on the number of 1 digits in the mask. Classless Inter-Domain Routing (CIDR) shorthand writes an IP address and its associated network mask in the form: xxx.xxx.xxx.xxx/n Here, n represents a number between 1 and 31 that is the number of 1 bits in the mask. CIDR supports classless IP addressing and associates network masks with IP network numbers independent of their traditional class. Routers that support CIDR recognize these networks as individual routes, even though they may represent an aggregation of several traditional subnets.

Network Classes

The InterNIC organization administers internet domain names and divides IP addresses into classes. The most common of these are classes A, B, and C. Class C networks use a default subnet mask of 255.255.255.0.

Using 255 255 255 0 as an IP Address

Although expressed in the form of an IP address number, network devices use 255.255.255.0 as a mask and not as a working IP address. Attempting to use this number (or any IP number that starts with 255) as a device address causes the IP network connection to fail due to the definition of number ranges on IP networks. Was this page helpful? Thanks for letting us know! Get the Latest Tech News Delivered Every Day Subscribe Tell us why! Other Not enough details Hard to understand Submit More from Lifewire IP Tutorial: Subnet Mask and Subnetting Classless Inter-Domain Routing Information What Is an IP Address? How to Use an IP Address to Find a MAC Address How to Find the Default IP Address of a Belkin Router How to Fix a "Failed to Obtain IP Address" Android Error HWiNFO v7.30 Review (A Free System Information Program) How to Look up an IP Address Owner When to Use a Static IP Address How to Find Your Xbox Series X or S IP Address How to Set Up Port Forwarding How to Change Your IP Address DNS Servers: What Are They and Why Are They Used? Why There Are Only 13 DNS Root Name Servers What Is a Public IP Address? (and How to Find Yours) How to Set Up a Router Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up By clicking “Accept All Cookies”, you agree to the storing of cookies on your device to enhance site navigation, analyze site usage, and assist in our marketing efforts. Cookies Settings Accept All Cookies