Internet Protocol (IP) address is an unique numeric identifier for a device, such as personal computers, printers, tablets, and smartphones, on the Internet. An IP address is used to identify a device and communicate with other devices in the IP network. Any device connected to the IP network must have an unique IP address within the network. An IP address is similar to a street address or a telephone number that is used to uniquely identify an entity. So we can say that an Internet Protocol address (IP address) is a numerical label assigned to each device participating in a computer network that uses the Internet Protocol for communication. It is a label indicating what we seek, and an address indicating where it is.
An IP address is written in “dotted decimal” notation. In IPv4 system, an IP address is divided into 4 sets of numbers separated by period. An example of IPv4 address is 189.45.28.89, each set representing 8-bit number ranging from (0-255).
IP addresses are managed by the Internet Assigned Numbers Authority (IANA), which assign the IP address space allocations globally and delegates five regional Internet registries (RIRs) to allocate IP address blocks to local Internet registries (ISP – Internet service providers) and other entities.
IPv4 and IPv6 IP Addresses
IPv4 Addresses, such as: 142.70.254.23. IPv4 (Internet Protocol Version 4) is an IP address as a 32-bit number. Today, most of devices on the Internet is addressed with IP version 4 (IPv4) addresses.
IPv6 Addresses, such as: 2001:db8:0:1234:0:567:8:1. IPv6 is a new version of IP, and it is a more recent protocol, offering a much larger address pool than IPv4. IPv6 uses 128 bits for the address. This IP system was developed in 1995, standardized as RFC 2460 in 1998, and its deployment has been ongoing since the mid-2000s.
IPv4 system with A 32-bit number is capable of providing about 4 billion unique numbers, and it is running out as more devices are connected to the Internet. IPv6 system offers much larger, virtually limitless number of unique addresses.
Private and Public IP Address
Private IP address, alternatively referred to as “local IP address”, “internal IP address”, is the IP address that is assigned by a local network router.
Often, a private IP address starts with 192.168.x.x. These IP addresses is not public, but only for internal use. For example, if in your local network that has 4 computers, then the computers may be assigned the private IP addresses like these: 192.168.0.10, 192.168.0.11, 192.168.0.12, and 192.168.0.13. These IP addresses are used to connect each other in the local network, and also used to receive and send information from/to the Internet.
Private networks can use IP addresses in the following 3 groups of ranges:
- 192.168.0.0 – 192.168.255.255 (65,536 IP addresses)
- 10.0.0.0 – 10.255.255.255 (16,777,216 IP addresses)
- 172.16.0.0 – 172.31.255.255 (1,048,576 IP addresses)
Private IP addresses are not reachable on the Internet. They can only be seen by other computers in the local network and not by any computers in an external network such as on the Internet.
Please note, there is another group IP addresses starting from 127.xxx.xxx.xxx where the xxx is between 1 and 255, such as 127.0.0.1. These are also private IP addresses, called “Loopback Addresses”:
- 127.0.0.0 – 127.255.255.255
To reach the Internet, a local network needs a public IP address, which is alternatively referred to as “external IP address”, “Internet IP address”. If you see an IP address that is different from the above four groups of IP ranges, then it is a public IP address, such as 146.45.89.103.