How a subnet is defined
An IP address contains network bits and host bits. The prefix length states how many leading bits identify the network. In IPv4, 192.0.2.0/24 uses 24 network bits and leaves 8 bits for addresses inside the subnet.
IPv4 networks may also use a subnet mask. The /24 prefix corresponds to 255.255.255.0. IPv6 normally uses prefix notation, such as 2001:db8:1234::/64.
How subnetting works
A device compares the network portion of its address with the destination address. If they match, it sends traffic directly over the local network. If they don’t, it sends the traffic to a router, usually its default gateway.
Subnet: 192.0.2.0/24
Address range: 192.0.2.0–192.0.2.255
Local example: 192.0.2.200
Outside example: 198.51.100.20A conventional IPv4 /24 contains 256 addresses. Its first address identifies the network and its last is the broadcast address, usually leaving 254 assignable host addresses. Special prefixes such as /31 and /32 follow different rules.
Subnet vs ASN
A subnet describes an address range. An Autonomous System Number identifies a network that announces routes under a common routing policy.
| Subnet | ASN | |
|---|---|---|
| Represents | One CIDR-defined address range | A network with one routing policy |
| Typical size | One prefix | May announce many prefixes |
| Main use | Addressing and local routing | Routing between networks |
Several subnets can belong to one ASN. A subnet also doesn’t determine location or connection type by itself.
Why subnets matter for proxies
A proxy changes the public exit IP a website sees, but several proxy IPs may share the same prefix. In proxy discussions, “subnet” often means a shared CIDR block rather than proof that the addresses are on one local network.
Websites, CDNs and firewalls can group traffic by prefix when applying rate limiting or reputation controls. Switching between two addresses in the same /24 therefore doesn’t guarantee that they’ll be treated independently. Sites can also evaluate the ASN, request rate, headers and browser behavior.
For public data collection, respect the site’s terms and published limits. Slow down when requests are limited instead of treating access to more subnets as permission to increase load.
FAQ
What does /24 mean in a subnet?
It means the first 24 bits identify the network. In IPv4, that leaves 8 bits for addresses within the subnet.
How many usable IP addresses are in a /24 subnet?
A /24 has 256 total addresses. A conventional IPv4 subnet usually provides 254 assignable host addresses after reserving the network and broadcast addresses.
Can a website block an entire subnet?
Yes. A website, CDN or firewall can block a CIDR range such as 192.0.2.0/24, affecting every address in that range. It may instead limit individual IPs or broader ASN ranges.