IPv4
This section is transcluded from IPv4#Special-use addresses. (edit | history)

IPv4 designates special usage or applications for various addresses or address blocks:[1][2]

Special address blocks Address block    Address range   Number of addresses     Scope   Description
0.0.0.0/8   0.0.0.0–0.255.255.255   16777216    Software    Current network[3]
10.0.0.0/8  10.0.0.0–10.255.255.255     16777216    Private network     Used for local communications within a private network.[4]
100.64.0.0/10   100.64.0.0–100.127.255.255  4194304     Private network     Shared address space[5] for communications between a service provider and its subscribers when using a carrier-grade NAT.
127.0.0.0/8     127.0.0.0–127.255.255.255   16777216    Host    Used for loopback addresses to the local host.[3]
169.254.0.0/16  169.254.0.0–169.254.255.255     65536   Subnet  Used for link-local addresses[6] between two hosts on a single link when no IP address is otherwise specified, such as would have normally been retrieved from a DHCP server.
172.16.0.0/12   172.16.0.0–172.31.255.255   1048576     Private network     Used for local communications within a private network.[4]
192.0.0.0/24    192.0.0.0–192.0.0.255   256     Private network     IETF Protocol Assignments.[3]
192.0.2.0/24    192.0.2.0–192.0.2.255   256     Documentation   Assigned as TEST-NET-1, documentation and examples.[7]
192.88.99.0/24  192.88.99.0–192.88.99.255   256     Internet    Reserved.[8] Formerly used for IPv6 to IPv4 relay[9] (included IPv6 address block 2002::/16).
192.168.0.0/16  192.168.0.0–192.168.255.255     65536   Private network     Used for local communications within a private network.[4]
198.18.0.0/15   198.18.0.0–198.19.255.255   131072  Private network     Used for benchmark testing of inter-network communications between two separate subnets.[10]
198.51.100.0/24     198.51.100.0–198.51.100.255     256     Documentation   Assigned as TEST-NET-2, documentation and examples.[7]
203.0.113.0/24  203.0.113.0–203.0.113.255   256     Documentation   Assigned as TEST-NET-3, documentation and examples.[7]
224.0.0.0/4     224.0.0.0–239.255.255.255   268435456   Internet    In use for IP multicast.[11] (Former Class D network.)
233.252.0.0/24  233.252.0.0-233.252.0.255   256     Documentation   Assigned as MCAST-TEST-NET, documentation and examples.[11][12]
240.0.0.0/4     240.0.0.0–255.255.255.254   268435455   Internet    Reserved for future use.[13] (Former Class E network.)
255.255.255.255/32  255.255.255.255     1   Subnet  Reserved for the "limited broadcast" destination address.[3][14]