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IPv4 networks commonly assign the subnet mask 255.255.255.0. Home routers and CCNA certifications often include it.
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255.255.255.0 and Subnetting
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Subnets split an extensive address range into smaller parts. They lower network traffic and manage access among subnets. A subnet mask shows these splits.
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Earlier subnets used classful networks, which grouped IP addresses into five categories (Class A, B, C, D, and E) based on the IP value.
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The 255.255.255.0 mask converts to binary as:
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- 11111111 11111111 11111111 00000000
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The zero bits in the mask represent the subnet’s address range, which covers 8 bits or up to 256 addresses.
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The table below shows that smaller subnetworks can be created by adjusting the mask.
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Subnet Details for 255.255.255 Prefix
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| Subnet Mask | Number of Subnets | Hosts Per Subnet |
| 255.255.255.252 | 64 | 2 |
| 255.255.255.248 | 32 | 6 |
| 255.255.255.240 | 16 | 14 |
| 255.255.255.224 | 8 | 30 |
| 255.255.255.192 | 4 | 62 |
| 255.255.255.128 | 2 | 126 |
| 255.255.255.0 | 1 | 254 |
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An incorrectly set subnet mask, called a netmask, might stop you from connecting to the internet.
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Subnets and CIDR
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The classful system wasted many IP addresses. Large companies and internet providers reserved big address blocks, preventing others from using them.
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In the 1990s, developers introduced classless IP networking to allocate addresses more efficiently and meet the growing demand for IPv4 addresses.
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Classless networks simplify traditional subnet masks. They use a shorthand based on the count of 1 bit in the mask. Classless Inter-Domain Routing (CIDR) uses this format:
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- xxx.xxx.xxx.xxx/n
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Here, n is a number from 1 to 31, showing how many 1 bits are in the mask.
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CIDR enables classless addressing. It links network masks to IP numbers without relying on their original class.
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Routers that support CIDR treat these networks as separate routes, even when they combine multiple traditional subnets.
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Network Classes
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The InterNIC organization names Internet domains and organizes addresses into different groups called classes. These classes include A, B, and C, which are the most commonly used.
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Each class has specific purposes for networking. Class C networks, for example, use a default subnet mask of 255.255.255.0, which helps to divide and manage network connections efficiently.
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IP classes are essential in determining how devices communicate within a network.
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The structure of these classes allows networks to be scalable and manageable, whether for small networks (Class C), medium-sized networks (Class B), or large-scale networks (Class A).
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Can 255.255.255.0 Be Used as an IP Address?
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Devices do not use 255.255.255.0 as an IP address, even though it looks like one.
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They use it as a subnet mask to define network and device ranges. Subnet masks like 255.255.255.0 help devices separate an IP address into their network and device sections.
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The connection will fail if you assign 255.255.255.0 or any IP starting with 255 to a device.
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IP networks reserve these ranges for special functions, such as broadcasting or network-specific tasks.
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