Worked examples

Read the block without guessing

These examples describe mathematical address intervals. Most ordinary examples use the documentation ranges from RFC 5737. They are illustrations, not destinations to contact or addresses assigned for your use. The inspector sends no probes.

A host address inside a /27

Enter 198.51.100.206/27. The result is canonical block 198.51.100.192/27, lowest address 198.51.100.192, highest 198.51.100.223 and count 32. The zero-based offset is 14 because 206 − 192 = 14. The entered address remains visible separately; the tool explicitly says that its remainder bits are nonzero.

A familiar /24

203.0.113.7/24 belongs to 203.0.113.0/24. Its numerical endpoints are .0 and .255, with count 256 and offset 7. The mask is 255.255.255.0. That count includes both endpoints and is deliberately not labeled usable hosts.

Two addresses in /31

192.0.2.255/31 has canonical lower address 192.0.2.254 and upper address 192.0.2.255. The count is 2 and offset is 1. The mask is 255.255.255.254. This result does not declare zero usable hosts: /31 point-to-point operation has specific rules outside a universal subtraction formula.

One address in /32

192.0.2.9/32 has the same entered, lower and upper address. Count is 1, offset is 0, mask is 255.255.255.255 and inverse wildcard is 0.0.0.0. The result is valid even though no remainder bits exist.

A /30 with a nonzero offset

198.51.100.14/30 spans 198.51.100.12 through 198.51.100.15. Four numerical addresses are included and the entered address has offset 2. The mask ends in 252, while the inverse wildcard ends in 3.

The complete /0 range

255.255.255.255/0 gives canonical block 0.0.0.0/0, endpoints 0.0.0.0 and 255.255.255.255, count 4,294,967,296 and offset 4,294,967,295. The page shows these exact values without constructing a giant address list. The mask is all zeroes and its inverse wildcard is all 255s.

High values stay unsigned

255.255.255.255/32 remains one address rather than becoming −1. At the other extreme, 0.0.0.0/32 also remains one address. These are numerical boundary checks, not statements about operational use.

Syntax errors stay visible

198.051.100.206/27 rejects because of a leading zero. 198.51.100.206/33 rejects because the prefix exceeds 32. Interior spaces, hostnames and dotted masks are also rejected. Invalid input clears the old block and export controls; correct it and explicitly inspect again, or reset the fixed example.