IP

IP is currently in-progress. You are viewing an entry that is unfinished.

The Internet Protocol (IP) provides for transmitting blocks of data called datagrams from sources to destinations, where sources and destinations are hosts identified by fixed length addresses. The internet protocol also provides for fragmentation and reassembly of long datagrams, if necessary, for transmission through "small packet" networks.

IPv4

Addressing

An IP (Internet Protocol) address is 32 bit, or four byte, address assigned to a specific machine that enables it to utilize the TCP/IP transport layer.

Because the highest value a Byte can be is 255 and the lowest is 0, this is the range of any "octet". Because an IP address contains four bytes, there are four octets in an ip address. The '0' value is reserved for the network, and the '255' value is reserved for what is called a broadcast. That means that IP addresses will typically not end in 0 or 255, because those numbers are reserved for other things.

Reserved Address Space & RFC 3330

127.0.0.0/8 - This is reserved in RFC 1700 and RFC 3330 for the local host. If you ever do anything to an IP address starting in 127, you will be performing these actions to your local machine.

192.168.0.0/16 - This is reserved in RFC 1918 for the local network. If you come across this type of IP address, it is not a machine out there on the internet, but one likely in your own house or another computer at the coffee shop you're hanging out in.

172.16.0.0/12 - This is reserved in RFC 1918 for the same as above

10.0.0.0/8 - Same as above

169.254.0.0/16 - This is a zeroconfig link-local address. Computers will automatically use an address in this block when they are set to use DHCP, yet there is no DHCP server on the network. This is defined in RFC 3927.

Obtaining Your IP Address

Local (LAN)

On Linux & Mac systems you can type:

ifconfig

or

ip addr show

On windows, you can type:

ipconfig /all

External (WAN)

You can check your router for the WAN address your ISP gave you, or just use one of the services available on the Web, like DuckDuckGo or ShowIP.

References

RFC 791