The /32 prefix means the first 32 bits of the address identify the network and the remaining 0 identify the host. Written out, the mask is 255.255.255.255, in binary 11111111.11111111.11111111.11111111, and its Cisco wildcard or inverse form is 0.0.0.0. It covers 1 addresses, of which 1 can be given to hosts.
| CIDR prefix | /32 |
|---|---|
| Subnet mask | 255.255.255.255 |
| Mask in binary | 11111111.11111111.11111111.11111111 |
| Wildcard (inverse) mask | 0.0.0.0 |
| Host bits | 0 |
| Total addresses | 1 |
| Usable hosts | 1 |
| Block size (magic number) | whole octet 4 |
A 192.168.1.0/24 contains 256 subnets of /32. Here are the first 8, which is enough to see the pattern: each one starts 256 after the last in octet 4.
| Network | First host | Last host | Broadcast |
|---|---|---|---|
| 192.168.1.0/32 | 192.168.1.0 | 192.168.1.0 | n/a |
| 192.168.1.1/32 | 192.168.1.1 | 192.168.1.1 | n/a |
| 192.168.1.2/32 | 192.168.1.2 | 192.168.1.2 | n/a |
| 192.168.1.3/32 | 192.168.1.3 | 192.168.1.3 | n/a |
| 192.168.1.4/32 | 192.168.1.4 | 192.168.1.4 | n/a |
| 192.168.1.5/32 | 192.168.1.5 | 192.168.1.5 | n/a |
| 192.168.1.6/32 | 192.168.1.6 | 192.168.1.6 | n/a |
| 192.168.1.7/32 | 192.168.1.7 | 192.168.1.7 | n/a |
A /32 falls exactly on an octet boundary, so there is no magic number to work out: octet 4 of the mask is 255 and every subnet starts where the previous one ended, counting octet 4 up by one.
A /32 is a single address. You use it for loopback interfaces, host routes, and any access list or firewall rule that needs to match one machine and nothing else. In routing it means "this exact host, nowhere else".
A /32 is a single address, so it holds exactly one host and has no network or broadcast address to reserve.
The /32 subnet mask is 255.255.255.255 in dotted-decimal notation.
The wildcard mask, also called the inverse mask, is 0.0.0.0. It is the bitwise inverse of 255.255.255.255 and is what Cisco access lists and OSPF network statements expect.
The /32 mask written out bit by bit is 11111111.11111111.11111111.11111111: 32 ones followed by 0 zeros.
A /24 splits into 256 subnets of /32.