NAT Basics with need,types of nat,configuration and Advantages of nat

Posted: 12 Nov 2017 in CCNA
Tags: , ,

In this tutorial we will learn the basics of NAT like NAT introduction,Advantages of NAT,Disadvantages of NAT,Types of NAT and NAT configuration;

NAT stands for Network Address Translation. Bydefault Private IP Address can’t access internet because internet uses public ip address.So if you want to access internet from a private ip address you must configure NAT.
NAT is used to communicate public ip address with private ip address and vice versa.
NAT allows a single device like Router to act as a agent between the Internet and Local Network.
So all IP Address Translations take place at Router.



CLASS A:   (       to
CLASS B:  (     to
CLASS C:  (   to

NAT also ac as a typical firewall by hiding Internal IP Address from outer network.


Public IP address sharing.
Easier expansion.
Greater Local Control.
Flexibility in ISP service.
Enhanced Security.
Mostly Transparent.



It’s complex to configure.
Lack of ip address creates problems.
Certain Applications are not compatible with NAT.
Problems with Security Protocol.
Poor support for client access.
Performance Reduction.
NON-NAT GIST nodes must be NAT aware.
Does not work in the presence of IPSec/TLS.


There are total mainly Three types of NAT
1.Static NAT
2.Dynamic NAT(DNAT)
3.Port Address Translation(PAT)


But very few network engineers also beleive that NAT can be of below types:

NAT which modify only IP addresses.
NAT which modify IP addresses and Port Numbers.
NAT that use a single IP Address.
NAT that Dynamically allocate IP Addresses to flows.

But if you are in ccna stage go with top 3 NAT i have mentioned above.




If anyone want to configure NAT then atleast one interface on the router has to be configured with Inside Interface using below command.

Router#configure terminal
router(config)#ip nat inside

Use the IP Nat outside command to mark as interface as an outside interface.

Router#configure terminal
router(config)#ip nat inside


 Read:How to configure STATIC NAT on IPv4

Read:How to configuer STATIC NAT on IPv6



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