// Networking
Subnet Calculator online
IPv4 CIDR subnet calculator - network, broadcast, host range, and more
by
CHUNKY
MUNSTER
MUNSTER
Subnet Calculator simplifies the process of carving up address ranges for network configuration. Whether you are calculating VLSM or setting up a simple supernet, this tool provides the network address, broadcast, and usable host range instantly.
Edge cases are handled correctly: /31 follows RFC 3021 and reports two usable hosts for point-to-point links, while /32 reports a single host for loopback or host routes. This network divider accepts both CIDR notation and dotted-decimal mask inputs, showing results in prefix and binary forms for easy integration into Cisco configs.
It's the bitwise inverse of the subnet mask, used in Cisco IOS access-control lists (ACLs) and OSPF area definitions. /24 has subnet mask 255.255.255.0 and wildcard 0.0.0.255 - the wildcard tells the device which bits to ignore when matching.
Traditionally /30 reserves the first address as the network and the last as broadcast, leaving 2 hosts. /31 (defined in RFC 3021) re-uses both addresses as hosts on point-to-point links - common between routers - also giving 2 usable addresses but no overhead.
A /32 represents a single host (a one-IP "subnet"). It's used in loopback interfaces, host routes and BGP advertisements where you specifically want to route a single address.
This tool is IPv4 only. IPv6 doesn't use broadcast (it uses multicast for similar functions), and the address arithmetic is done in 128-bit integers - see a dedicated IPv6 subnet calculator for that work.
Explore the full suite of Networking tools and 290+ other free utilities at Chunky Munster with our Subnet Calculator.