Public and Private IP addresses explained. What is NAT.

Any networked device (computer, server, printer, router etc), needs an IP address to communicate either on the Internet or on its local area network (LAN). Especially for internet communication, this IP address has to be unique, in order to avoid address conflicts. The IP address that is used by a device to communicate on the Internet is called “Public” address, and it is registered with the Internet Network Information Centre (InterNIC) which takes care of the uniqueness factor. We could have only “Public” IP addresses assigned to all network devices, but this is not possible since the current IP address range (32-bit addresses for IPv4) is not enough to cover all network nodes. Therefore, the Internet network community (IETF etc) has established three “Private” address ranges, which can be given to network devices that belong to a local private network which does not connect directly to the Internet cloud.

These “Private” address ranges are the following:

  • From to
  • From to
  • From to

Now, the most common practice today for Network engineers is to assign private IP addresses to devices in their private Local networks, and use Network Address Translation (NAT) if a device needs to access the Internet. The purpose of NAT is to translate the source private IP address of the network device into a public IP address in order to communicate with another host on the Internet. Since NAT allows many-to-one IP translation, you can have many private IP addresses translated to a single public address, thus saving address space.

Computer Networks Overview

The term networks (communication networks) generally refers to systems hardware, software and services / opportunities, aimed at transmission and routing data and to transfer information between electronic / channels (such as various types of computers, terminals, telephones) .

The term includes the various technologies

  • telecommunications networks
  • computer networks (local (LANs), Metropolitan (MANs), wide area (WANs) and Websites)
  • integrated services digital networks close (N-ISDN) and large B-ISDN) zone, and all wireless communication technologies.

For the classification of networks can be used several characteristics: Continue reading “Computer Networks Overview”

What is Virtual Private Network (VPN)

This online quiz is a series of essential questions about VPNs. Although many of the technical details of VPNs are hidden from the casual user, several aspects of the technology directly affect the “user experience,” and it is important to understand these.

Students, networking professionals, corporate employees, and anyone else interested in the basic technology of computer networks should find this a valuable study guide. Continue reading “What is Virtual Private Network (VPN)”

How to access remotely your internal network

Remotely Accessing your internal network and data is sometimes mandatory and can be used for a variety of reasons. Maybe you are outsourcing some of your business to an external partner, maybe you require external technical support, or you may have employees on the road or tele-workers that require access to internal data and resources in your company. In any case, you must take measures to protect your data and network, but still keep the operation of your remote access service as functional as possible.

In this article I describe the most popular methods and technologies available to use in order to enable your company users to access internal data from outside your company. Continue reading “How to access remotely your internal network”

The Base of TCP/IP Networking

A few years ago there was a big hype about “being online”. Everyone had to be online and there wasn’t one day where you didn’t have to be afraid that you missed the coolest and newest technology. This was just the TCP/IP layer and it was already well known for over 20 years back then.

So what is this TCP/IP thing? What good does it do for you and has this been the latest thing or will it even get better? This article is trying to touch some of the aspects of the TCP/IP layer, higher level protocols based on it and give a brief outlook on what is next. Continue reading “The Base of TCP/IP Networking”