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Calculate an IPv4 network, subnet mask, broadcast address and address range from an address and CIDR prefix.
CIDR prefix is a bit count, not a dotted mask. Calculations and controls run in this browser tab.
CIDR separates the leading network bits from the remaining host bits. For 192.168.1.123/24, the first 24 bits are the network; masking gives 192.168.1.0, mask 255.255.255.0 and broadcast 192.168.1.255. The conventional assignable range is 192.168.1.1–192.168.1.254. RFC 4632 defines prefix notation and explicitly permits lengths from 0 to 32.
A /24 block has 2^(32−24) = 256 total addresses. In ordinary IPv4 subnetting, network and directed broadcast addresses are not assigned to hosts, leaving 254. A /31 is different: RFC 3021 permits both addresses on a point-to-point link. A /32 is a single host route. This calculator reports usable counts accordingly, but your network hardware or provider may impose additional restrictions.
The result is mathematical IPv4 block arithmetic. It does not check whether addresses are allocated, public, private, reachable or safe to expose. Some modern networks do not use directed broadcast in the simple historical way. IPv6 uses a different address length and is not supported here. Verify routing, reservations and gateway choices in the real deployment before changing a production network.
Example: 192.168.1.123/24 belongs to network 192.168.1.0/24 with mask 255.255.255.0.
Use the sample inputs above to reproduce the example. Results display practical rounded values; real measurements and agreements can involve more uncertainty than the arithmetic.
255.255.255.0.
Conventionally 254 after excluding network and broadcast.
RFC 3021 defines two-address point-to-point links.
No. It only computes address-block arithmetic.
Last reviewed: November 1, 2026. Verify source conditions, local requirements, and product or contract terms before consequential decisions.
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