CIDR (Classless Inter-Domain Routing) is a method for allocating IP addresses and routing traffic using variable-length subnet prefixes instead of fixed address classes. It is written as an IP followed by a slash and prefix length (e.g., 10.0.0.0/8).
CIDR replaced the old classful addressing system (Class A, B, C) with flexible prefix lengths. The number after the slash indicates how many bits define the network portion. A /24 prefix means the first 24 bits are the network, leaving 8 bits (256 addresses) for hosts. A /16 prefix covers 65,536 addresses. This flexibility allows efficient allocation of IP blocks to organizations of any size.
Most proxy users only need to understand this well enough to debug it, not configure it directly.
USER-country-de-session-task01The username carries the config: "country-de" picks the exit, "session-task01" holds it in place while CIDR does its work underneath. No separate API call or handshake -- the label is the setting.
Measure this metric without a proxy first, so you know what the gateway adds versus what was already there.
This concept governs the connection to the gateway and the gateway to the target -- check both when something looks wrong.
KnoxProxy manages this at the infrastructure layer, so most jobs only need to understand it well enough to debug.
A new ISP, VPN, or office network can change how this behaves -- confirm it again after any local network change.
A proxy provider purchases a /22 CIDR block (1,024 IPs) from a regional registry and distributes them across multiple proxy servers for subnet diversity.
CIDR notation appears in proxy documentation, IP allowlists, and network configuration. Understanding it helps you read proxy specifications and configure IP-based access controls correctly.
A /24 means the first 24 of 32 bits in an IPv4 address are the network portion. This creates a block of 256 IP addresses (254 usable for hosts). It is equivalent to a subnet mask of 255.255.255.0.
Proxy providers describe their IP distribution using CIDR blocks. IPs from many different /24 blocks (high subnet diversity) are harder to block en masse than IPs from a single contiguous /16 block.
Ready to put this into practice? Network Documentation
Start a free trial and test with real targets -- no credit card, no sales call.