Why does a /24 have 254 hosts, not 256?

The network address (all host bits 0) and the broadcast address (all host bits 1) cannot be assigned to hosts. 256 total minus 2 reserved equals 254 usable.

RFC 3021 defines /31 for point-to-point links: both addresses are usable hosts, no broadcast. A /32 is a single host, used by loopback interfaces and route advertisements.

What is a wildcard mask?

The bitwise inverse of the netmask. Cisco ACLs expect wildcard masks instead of netmasks — the tool shows both so you can copy whichever your config needs.

Subnet Calculator

Type an IPv4 CIDR like 192.168.1.0/24 and see every derived field — network, broadcast, host range, netmask, and wildcard.

IPv4 CIDR

Try 10.0.0.0/8, 172.16.5.100/20, or 198.51.100.42/27.

Network

192.168.1.0/24

254 usable hosts · 256 total addresses · Class C

Netmask

255.255.255.0

Wildcard

0.0.0.255

First host

192.168.1.1

Last host

192.168.1.254

Broadcast

192.168.1.255

Prefix

/24

Binary mask

11111111.11111111.11111111.00000000

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