A subnet is a range of IP addresses that share a common prefix — used to organise networks and route traffic.
Explanation
IP addresses are typically allocated in subnet-sized blocks. A /24 subnet contains 256 addresses (like 192.0.2.0/24 → 192.0.2.0 through 192.0.2.255). A /16 contains 65,536. Firewalls and routing systems operate at subnet granularity — "block this whole /24" is one rule rather than 256. Cloud providers allocate subnets to their VM ranges, and reputation systems fingerprint entire subnets as "known datacenter". When a proxy operator gets one IP flagged, often the whole subnet gets flagged with it — which is why proxy services rotate addresses across many subnets.
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