NAT Introduction and basic configuration on a Cisco Router

What is NAT?

NAT is short for "Network Address Translation". The basic purpose of NAT is to translate private IP addresses which are used inside the company into public (global) IP addresses.

NAT is primarily used to conserve global IP addresses because it allows that many IP-enabled devices use a few public IP addresses. It's really easy to see NAT at work. For instance, at your work place you and your colleagues are probably represented by a single IP address and NAT allows you all to access the Internet at the same time.

To verify all this simply go on some What's my IP? service from yours and your friend's computer, and you'll see that you and your friend have the same IP address. In reality the address you see is the address of a router that runs NAT.

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DHCP makes our lives easier

As we all know, if the computers want to communicate with each other, they must be on the same network. In addition, every computer must be assigned an IP address. In large networks this can take a significant portion of administrator's and users' time, not to mention the possibility of assigning duplicate addresses and lost connectivity. And even if you configure everything correctly, it's difficult to add new hosts to the network. Or what if the employee moves to another part of a building? DHCP to the rescue!

What is this DHCP and where is it used?

DHCP stands for Dynamic Host Configuration Protocol. DHCP is a protocol that's used on to automatically configure the hosts on a network. In addition to configuring the hosts with an IP address, DHCP can also configure them with additional parameters, such as subnet mask, or DNS server address.

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Why you should be using GNS3 and How to start

I have been mentioning the GNS3 for last 2 Networking blog posts and still using Cisco Packet Tracer to show network topologies and Router Configurations. So, I believe the time has finally come to say a few words about GNS3.

After this, I will be able to use GNS3 in some future blog post about networking and not feel bad about it. :)

What is GNS3?

GNS is a shorthand for Graphical Network Simulator. GNS3 allows you the emulation of network hardware on your PC, similar to Windows Virtual PC. Windows Virtual PC enables you to run operating systems inside the virtual environment. You may have heard of Windows XP mode in Windows 7 for example.

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Introduction to Routing

As you may or may not know, communication on the Internet uses packets for transmitting data. So, every time your computer communicates with a computer on the Internet, IP packets are used to transmit and receive data.

Your computer by itself can’t deliver the packets all the way to the destination, so it relies on other networking hardware on the way over to do their part. We could say that Routing is a process of selecting the best paths through the network for forwarding packets from source to their destination.

I have to communicate with another computer! But he’s not in the same network as me! What do I do? Send the packets to the my default gateway! He IS in my network and hopefully, he WILL know what to do! :)

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Virtual LANs - Introduction and basic operations

„VLANs? That doesn’t sound like a Web Design or Development theme!” And you’re right! From now on, I’m adding Networking to the Blog categories, and VLANs are going to be my first post.

Virtual? LAN?

Of course, we all know what a LAN is. It is a network which connects computers and other devices and is typically located in our home or office building. LAN enables our devices to share data with each other and access each others resources.

So, LANs are cool, but as always, there’s a room for some improvement. Imagine your company has marketing, production and management departments. In a traditional LAN sense you would have to either:

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