Reserved IP addresses
In the Internet addressing architecture, the Internet Engineering Task Force (IETF) and the Internet Assigned Numbers Authority (IANA) have reserved various Internet Protocol (IP) addresses for special purposes. These IP addresses may be used for maintenance of routing tables, multicast, operation under failure modes, or to provide addressing space for public, unrestricted uses.
The IETF sets the guidelines for use of the IP address space in RFC specifications, and directs IANA to implement the policies. Reserved IP addresses tend to belong to three categories: addresses that are globally unique, addresses that are unique to the subnet, and addresses that are only relevant to the host using the address.
Reserved IPv4 addresses
|CIDR||Address Range||Number of Addresses||Scope||Purpose|
|16,777,216||software||Used for broadcast messages to the current ("this") network as specified by RFC 1700, page 4.|
|16,777,216||private network||Used for local communications within a private network as specified by RFC 1918.|
|4,194,304||private network||Used for communications between a service provider and its subscribers when using a Carrier-grade NAT, as specified by RFC 6598.|
|16,777,216||host||Used for loopback addresses to the local host, as specified by RFC 990.|
|65,536||subnet||Used for autoconfiguration 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, as specified by RFC 6890.|
|1,048,576||private network||Used for local communications within a private network as specified by RFC 1918|
|8||private network||Used for the DS-Lite transition mechanism as specified by RFC 6333|
|256||documentation||Assigned as "TEST-NET" in RFC 5737 for use solely in documentation and example source code and should not be used publicly.|
|256||Internet||Used by 6to4 anycast relays as specified by RFC 3068.|
|65,536||private network||Used for local communications within a private network as specified by RFC 1918.|
|131,072||private network||Used for testing of inter-network communications between two separate subnets as specified in RFC 2544.|
|256||documentation||Assigned as "TEST-NET-2" in RFC 5737 for use solely in documentation and example source code and should not be used publicly.|
|256||documentation||Assigned as "TEST-NET-3" in RFC 5737 for use solely in documentation and example source code and should not be used publicly.|
|268,435,456||Internet||Reserved for multicast assignments as specified in RFC 5771.
18.104.22.168/24 is assigned as "MCAST-TEST-NET" for use solely in documentation and example source code.
|268,435,455||n/a||Reserved for future use, as specified by RFC 6890.|
|255.255.255.255/32||255.255.255.255||1||n/a||Reserved for the "limited broadcast" destination address, as specified by RFC 6890.|
Reserved IPv6 addresses
|CIDR||Address Range||Number of Addresses||scope||Purpose|
|::1/128||::1||1||host||loopback address to the local host.|
|232||software||IPv4 mapped addresses|
|264||Discard Prefix RFC 6666|
|232||global Internet||IPv4/IPv6 translation (RFC 6052)|
|2100||software||Overlay Routable Cryptographic Hash Identifiers (ORCHID)|
|296||documentation||Addresses used in documentation|
|2121||private network||Unique local address|
- RFC 6052 section 3.2