What is a subnet?

A subnet is a range of IP addresses that forms one section of a network, such as 192.168.10.0 to 192.168.10.255 for the office and another range for servers. Splitting a network into subnets, usually together with VLANs, groups devices and lets the router or firewall control traffic between groups. Administrators write subnets in a short form like 192.168.10.0/24, where the number after the slash says how big the range is. In security reports, a scan of a subnet means one device knocked on many addresses in that range, often a sign that someone is mapping the network.

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