How to Use NAT Network Fundamentals (Part 21)

We have a lot of private IP address in our networks. But, we can only use public IP addresses on the internet. So how can our privately-addressed devices access the publicly-addressed internet? With a technology called Network Address Translation, or NAT.
NAT has the ability to rewrite the source and/or destination IP address in the IP header. A complimentary technology called Port Address Translation (PAT) can change the source and destination ports in a TCP or UDP header.
A NAT can by static or dynamic. A static NAT will match an original IP with the same translated IP every time. Dynamic NAT on the other hand, will use a different mapping each time.
Sometimes we don’t have enough public IP’s to map to, so we will need to use a different aspect of NAT, called port overloading. This is sometimes called masquerading.
Port overloading lets us assign a different port number to each translation, so we can conserve the number of public IP’s that we’re using.
A key concept in NAT is understanding where the traffic starts from. Is it starting within the network, and heading out? Or is is starting somewhere on the internet, and heading into our network.
This makes it easier to understand bidirectional and unidirectional NAT.
Be sure to check out the labs (links below) if you want to try this out yourself.
Overview of this video:
0:00 Introduction
0:27 What is NAT?
1:41 How NAT Works
5:07 Configuring Static NAT
9:24 Configuring Dynamic NAT
13:15 Port Address Translation
16:20 Port Overload
Quiz Link: https://networkdirection.net/labsandquizzes/quizzes/network-address-translation-nat-quiz
Lab Challenge 1: https://networkdirection.net/labsandquizzes/labs/lab-network-address-translation
Extra reading: https://www.ciscozine.com/nat-virtual-interface-aka-nvi-what-is-that/
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