nat (outside,outside) dynamic interface, equivalent in IOS

Answered Question
Oct 14th, 2012

For a remote vpn user who just want to access the internet for now. now I know you have to put the following in config when using ASA, what is the equivalent in IOS?

nat (outside,outside) dynamic interface.



Correct Answer by Harish Balakrishnan about 4 years 4 months ago

Hello Han,

you are correct.!


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Harish Balakrishnan Sun, 10/14/2012 - 22:46


I think you wanted to achieve hairpinning for the ipsec remote access vpn users to access internet via vpn router..There is no direct way of doing this like we have in ASA.

Please follow the below cisco document where you can make use of nat on a stick configuration to achieve.. this



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Harish Balakrishnan Mon, 10/15/2012 - 10:51

Hello Han,

No it is not a typo.. since the next hop ip is belongs to loopback interface, the route map will send the traffic to loopback interface ( that is ultimately we wanted router to do to imitate the inside interface.

the problem is ' for a nat to happen, the traffic has to go throug an inside and outside interface', so we are just faking the inside interface with the help of loopback !



hanwucisco Mon, 10/15/2012 - 11:44

So, you mean it sends to an ip address that is not configured in the network but belongs to the subnet of the Loopback's.
So that the traffic is "tricked" to the loop interface?



abcdrohan Mon, 10/15/2012 - 05:40

nat (outside) 1

global (outside) 1 interface

Assuming is the ip pool assigned to the RA vpn

Rudy Sanjoko Mon, 10/15/2012 - 05:49

On IOS, you will need to create a pool for the dynamic interface using  "ip nat pool" command then use "ip nat outside pool ",  after that you will need to implement it on the interface. I left out  some other parameters to make it easier for you to compare the NAT on  ASA and on IOS.

Harish Balakrishnan Mon, 10/15/2012 - 10:33

  Hello ,

This is just an IP under loopback interface,

When traffic comes in through outside interface, it has to go through an inside & outside Nat  in order to access internet,so what we are doing is to forcefully send the the traffic to loopback ( where we have ip nat inside configured - and it will undergo nat inside process) once it comes back to routing table then it will check the default route to go outside, ( this time nat outside process and we are good)..

Please shoot if you have any query.



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