IP
Internet Protocol (IP) is a communications protocol for routing across networks. Machines are assigned an Internet Protocol Address (IP address) to which packets are addressed.
Contents
Addresses
An IP address is a unique 32-bit or 128-bit number, for IPv4 and IPv6 respectively.
Addresses can either be static or dynamically assigned. The predominant method for assigning dynamic addresses is DHCP.
Reserved Addresses
A set of addresses are reserved for local networking:
IP Block |
IP Range |
Reserved for |
127.0.0.0/8 |
127.0.0.0 - 127.255.255.255 |
Loopback |
10.0.0.0/8 |
10.0.0.0 - 10.255.255.255 |
Local network |
172.16.0.0/12 |
172.16.0.0 - 172.31.255.255 |
Local network |
192.0.0.0/24 |
192.0.0.0 - 192.0.0.255 |
Local network |
192.168.0.0/16 |
192.168.0.0 - 192.168.255.255 |
Local network |
::1/128 |
::1 (yes, just one address) |
Loopback |
fc00::/7 |
fc00:: - fdff:ffff:ffff:ffff:ffff:ffff:ffff:ffff |
Local network |
There are also a number of reservations for infrastructure and future use. The remainder are mapped to the public internet.
Networks
Most networks are Local Area Networks (LAN). A LAN should restrict itself to the set of addresses reserved for local addressing, but there is no reason for local addresses to be globally unique.
A gateway stands between the LAN and the Wide Area Network (WAN). The Internet Assigned Numbers Authority (IANA) manages the assignment of addresses in this space.