Subnet /30: Mask 255.255.255.252, 2 Hosts for P2P Links
Calculate the network address, broadcast, subnet and wildcard masks, host range and usable host count for any IPv4 address and CIDR prefix.
Processed entirely in your browser — nothing you enter here is ever uploaded.
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About this tool
A /30 prefix keeps 30 of the 32 IPv4 bits for the network and leaves only 2 bits for hosts — the smallest classic subnet that still has usable addresses. Network engineers reach for it constantly: a point-to-point link between two routers needs exactly two addresses, one per interface, and a /30 provides precisely that with no waste beyond the two reserved addresses.
The subnet mask is 255.255.255.252. Two host bits give 2^2 = 4 addresses, and after the network and broadcast addresses are set aside 2^2 − 2 = 2 usable hosts remain. In 10.0.0.4/30, for example, the network address is 10.0.0.4, the two usable hosts are 10.0.0.5 and 10.0.0.6, and 10.0.0.7 is the broadcast. Modern gear can squeeze links into /31 (RFC 3021), but /30 remains the safe, universally supported choice.
This page opens the subnet calculator with /30 preselected: enter any IPv4 address and it aligns it to the enclosing /30 block, showing the network, broadcast, wildcard mask 0.0.0.3 and both usable hosts. Everything is computed with 32-bit integer math right in your browser — private, instant and available offline once the page has loaded.
Example. 172.16.5.20/20 resolves to network 172.16.0.0, broadcast 172.16.15.255, and 4094 usable hosts.
Limit. Only IPv4 addresses and CIDR prefixes are parsed.