What is Subnet?
A subnet is a contiguous block of IP addresses that shares a common network prefix, defined in CIDR notation such as 203.0.113.0/24. The prefix length says how many leading bits are fixed; the remaining bits enumerate the addresses inside the block. Subnets are the basic unit of IP allocation, routing, and — importantly for proxies — reputation and blocking.
How subnets work
CIDR (Classless Inter-Domain Routing) notation writes a subnet as a base address plus a prefix length: 203.0.113.0/24 means the first 24 bits are fixed and the last 8 bits vary, giving 256 addresses from .0 to .255. The same idea scales up and down — a /16 spans 65,536 addresses, a /28 just 16.
The prefix is what routers actually work with. Instead of storing billions of individual addresses, routing tables hold prefixes and forward each packet to the most specific match. Registries allocate large blocks to ISPs and hosting companies, which subdivide them into smaller subnets for customers, data centers, and internal segments.
In traditional IPv4 subnetting, the first address in a block identifies the network and the last is the broadcast address, so a /24 offers 254 usable host addresses. Subnet masks such as 255.255.255.0 are an older way of writing the same /24 boundary.
Why subnets matter for proxies and scraping
Anti-abuse systems frequently act on whole subnets rather than single addresses. If several addresses in one /24 misbehave, the entire block may be rate-limited or banned, since operators of proxy or hosting infrastructure usually control contiguous ranges and can trivially hop between neighboring addresses. Datacenter proxies are especially exposed: they often sit in well-known hosting blocks that one firewall rule can cover entirely.
This makes subnet diversity a real quality metric for proxy pools. Addresses scattered across many unrelated consumer subnets and networks are far harder to block in bulk without collateral damage; ProxyOmega's rotating unlimited-residential pool, for example, draws on 1.5M+ home IPs spread across consumer ranges rather than contiguous blocks.
Practical notes and common misconceptions
The slash number runs opposite to intuition: a smaller prefix length means a bigger network, so a /16 contains 256 times more addresses than a /24. The old class A/B/C terminology maps roughly to /8, /16, and /24 but has been obsolete since CIDR replaced classful addressing in the 1990s.
Subnet-level blocking is a blunt instrument. Banning a consumer /24 can lock out hundreds of unrelated households, which is why sites reserve aggressive block rules mostly for hosting and datacenter ranges and treat consumer subnets with more caution.
Subnet, answered
What does /24 mean in an IP address?
/24 suffix is CIDR notation meaning the first 24 bits of the address are the network prefix. That leaves 8 bits for hosts, so a /24 covers 256 consecutive addresses, for example 203.0.113.0 through 203.0.113.255. A smaller prefix number, like /16, describes a larger block.Why do websites block entire subnets instead of single IPs?
Related terms
Theory covered. Now route something. Start free.
Residential, ISP, mobile and IPv6 networks under one account — test the concepts on real infrastructure.
ProxyOmega