What does /24 or /64 after an IP address mean?¶
The number after the slash is a prefix length. It describes how much of the address identifies the network range.
A simple example¶
192.0.2.40/24 places the individual address 192.0.2.40 inside the wider 192.0.2.0-192.0.2.255 range. The /24 is the neighbourhood boundary; it is not the individual address.
IPv6 uses the same principle. A /64 normally identifies the first 64 bits as the network prefix and leaves the remaining 64 bits for addresses within that network.
A registration or routing result for a prefix may describe the organisation responsible for the range, not the subscriber or device using one address inside it. Providers may announce a large block, delegate smaller prefixes and assign individual addresses to different services.
Preserve the complete individual IP. Replacing it with a /24, /64 or other range loses specificity and may combine unrelated systems.
The point to remember
A prefix describes the size of a network range. It does not show that every address in that range belongs to the same device, subscriber or person.
