Subnet Calculator: Understanding CIDR, Network Ranges, and Subnetting
CIDR Notation Explained
CIDR (Classless Inter-Domain Routing) notation expresses a network as an IP address followed by a slash and prefix length: 192.168.1.0/24. The prefix length (24) indicates how many bits are the network portion. /24 = 256 addresses, 254 usable hosts. /16 = 65,536 addresses. /32 = single host.
Common Subnet Sizes
/30: 4 addresses, 2 usable — used for point-to-point links. /28: 16 addresses, 14 usable. /24: 256 addresses, 254 usable — standard small office network. /22: 1,024 addresses, 1,022 usable. /16: 65,536 addresses — large enterprise network. /8: 16.7 million addresses — ISP-scale.
Network vs. Broadcast Address
The first address in any subnet is the network address (not assignable to hosts). The last address is the broadcast address (not assignable to hosts). Usable hosts = total addresses − 2. Example: 192.168.1.0/24 → network 192.168.1.0, broadcast 192.168.1.255, usable: .1 through .254 (254 hosts).
Frequently Asked Questions
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