Private IP Addresses

A private IP address (also known as a "local IP address") is an internal address that is not routed on the internet and that only works within a local area network, unlike a public IP address which is a computer's "passport to the internet" and it is used to communicate outside the network.

From an Internet Service Provider's (ISP) perspective, one of the original reasons for using private IP addressing after allocating address blocks of public IP addresses from an RIR was the conservation of IP address space. Public Domain Name System (DNS) database records are usually not allowed to reveal private IP addresses.

Both public IP addresses and private IP addresses help to uniquely recognize a machine connected to the internet. The differences between the two are:

• A public IP address is a global IP address used to help devices communicate outside a network (for instance, to access the World Wide Web). This IP receives traffic straight from the internet and can be seen by someone on the other end of someone's online activity.
• Private IP address is an internal IP address that keeps local devices connected within a closed private network, excluding any online routing. It's impossible to access the internet by using a private IP address alone. The connection can be made via the Network Address Translation (NAT) to externally "translate" (configure) the private IP into a public one.

The fact that private IPs aren't directly linked to outside networks (internet included) leads to the following advantages:

• Enhanced data protection and privacy.
• Increased security (zero exposure to external threats).
• Network design flexibility (more address space available).
• Self-Containment (not vulnerable to external technical difficulties).
• Disadvantages:
• Isolation (as it is non-routable through the internet).
• Increased configuration and maintenance costs.

The Internet Assigned Numbers Authority (IANA) reserves the following private address ranges for in-house subnetting use through a router or other Network Address Translation (NAT) devices:

• 10.0.0.0 to 10.255.255.255 (could cover over 16 million addresses).
• 169.254.0.0 to 169.254.255.255 (for Automatic Private IP Addressing (APIPA) use only).
• 192.168.0.0 to 192.168.255.255 (could allow over 65,000).
• 172.16.0.0 to 172.31.255.255 (enables more than one million local addresses).

Both IPv6 and IPv4 specifications define private IP address ranges and address allocation for private internets. Most home and business routers worldwide have 192.168.1.1 IP address ranges that assign IPs like 192.168.1.2, 192.168.1.3, etc., to the various devices connecting to it via Dynamic Host Configuration Protocol (DHCP).

Establishing the type of IP, that's best for you or your corporate network depends on your specific circumstances (personal/business) and the importance you give to internet connectivity. There could be several scenarios:

• If you need several devices to communicate autonomously without relying on any human interaction with their in-house IP network, a fixed private IP address is exactly what you need.
• If you don't want to interact with your machine, a dynamic IP address is the answer.
• If you require unrestricted communication and complete access to machines via the www, a fixed public IP address would be the right solution.
• If you need internal network communication AND remote access to devices for configuration, a fixed IP with a VPN works just right.