Category Archives: NAT

Network Address Translation (NAT) & Scenario

Configuration Notes:
Defining NAT Inside and Outside Interfaces
The first step to deploy NAT is to define NAT inside and outside interfaces. You may find it easiest to define your internal network as inside, and the external network as outside. However, the terms internal and external are subject to arbitration as well. This figure shows an example of this.

NAT Overloading
Also called Port Address Translation (PAT) is form of dynamic NAT where we have is just a single inside global IP address providing Internet access to all inside hosts. As a general case, NAT Overload is used in scenarios where the number of inside local addresses is greater than the number of inside global addresses.

Clearing Static NAT Entry
Clear command will just delete dynamic entries. If you don’t need a static entry anymore, delete it in the config.
It will not be possible to clear static NAT entry that’s the reason why error message is seen “Translation not dynamic”. If the static NAT entry is not useful/not doing intended purpose, why not just editing or removing it.


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NAT Basics

NAT BASICS

static nat
ip nat inside source static 10.0.0.2 112.1.1.5

R4#sh ip nat translations
Pro Inside global Inside local Outside local Outside global
— 112.1.1.5 10.0.0.2 — —

R4#sh ip nat translations
Pro Inside global Inside local Outside local Outside global
icmp 112.1.1.5:5 10.0.0.2:5 112.1.1.2:5 112.1.1.2:5
icmp 112.1.1.5:6 10.0.0.2:6 112.1.1.2:6 112.1.1.2:6
icmp 112.1.1.5:7 10.0.0.2:7 112.1.1.2:7 112.1.1.2:7
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NAT Traversal

NAT Traversal
Network address translator traversal is a computer networking technique of establishing and maintaining Internet protocol connections across gateways that implement network address translation (NAT).

NAT traversal techniques are required for many network applications, such as peer-to-peer file sharing and Voice over IP.

https://en.wikipedia.org/wiki/NAT_traversal#Hosted_NAT_traversal

How Does NAT-T work with IPSec?
https://supportforums.cisco.com/t5/security-documents/how-does-nat-t-work-with-ipsec/ta-p/3119442