RFC 1918 Private Space
Definition
Three IPv4 ranges reserved for private use: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16. Not routable on the public internet; require NAT at the edge.
- Range 1
- 10.0.0.0/8
- Range 2
- 172.16.0.0/12
- Range 3
- 192.168.0.0/16
- Routability
- Not routable on the public internet
Common questions
Why does an investigator need to know a device's private range when reviewing network logs?+
Private addresses are reused across many unrelated networks, so a bare private IP in a log is only meaningful together with the NAT mapping, timestamp, and the specific network or ISP context that assigned it at that time.
How does NAT relate to these private ranges in an investigation?+
A gateway performing NAT translates an internal private address to a single public address for outbound traffic, so external logs only show the public address, and the NAT device's own translation logs are needed to identify which internal host was responsible.
Can two organisations legitimately use the identical private IP range at the same time?+
Yes, because these ranges are reserved for private use only and are not globally unique, many separate networks can and do reuse the same 192.168.x.x or 10.x.x.x addressing scheme without conflict.
Related terms
- CIDR (Classless Inter-Domain Routing)
- A compact notation for IP address ranges that appends a prefix length to the address, such as 192.168.1.0/24. The prefix length states...
- MAC Address (OUI)
- 48-bit hardware address. First 24 bits are the Organisationally Unique Identifier assigned by IEEE to a vendor; the lower 24 are the...
- OSI Reference Model
- Seven-layer ISO/IEC 7498-1 model describing how network functions are partitioned: Physical, Data Link, Network, Transport, Session, Presentation, Application. A teaching model, not...
- SLAAC
- Stateless Address Autoconfiguration. IPv6 host generates its own address from the router-advertised /64 prefix plus a 64-bit interface identifier (EUI-64 or RFC...
- TCP/IP Stack
- Four-layer model that actually runs the internet: Link, Internet, Transport, Application. Defined by the IETF and mapped onto the OSI layers for...