Nat in router or firewall?

Answered Question
Mar 19th, 2010

hi,

  could anyone confirm if doing the NAT in the router is better that doing it in a firewall?because someone told me this is the best practice from cisco.

My topology below:

CoreSwitch==>edge switch-->ASA-->Boarder router

Note: i have server in dmz configured in ASA and accessible thru internet.

thanks.

reymon

I have this problem too.
0 votes
Correct Answer by Kureli Sankar about 6 years 8 months ago

configuring policy nat, dynamic nat, nat exemption, outside nat, destination nat, static 1-1, policy static all of these can be easily done on the ASA.

I would say do the nat on the ASA and let the router do what is is betst to do which is routing.

-KS

Correct Answer by Jennifer Halim about 6 years 8 months ago

I guess it really depends on what you will be using the NAT for, as there is a number of application inspection that ASA is more superior of.

For example:

You are NATing your FTP server, and ASA is configured to inspect FTP traffic so it will dynamically open a pin hole for the FTP data connection.

If you perform the same on the router, first of all, for tighter security, you would need to create access-list, and then either CBAC or ZBFW to inspect the traffic. Router main functionality is performing routing, with the above example, you have just added security feature on the router which is not very efficient since you already have ASA firewall.

Hope that helps.

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Jennifer Halim Fri, 03/19/2010 - 05:15

Don't see the difference configuring it on router or ASA. Most people configured NAT on their ASA.

Mhon Baul Fri, 03/19/2010 - 06:38

Here is what they say:

Cisco Validated Design and best practices recommended dedicating only security features on the ASA. And they propose removing current NAT on the ASA and putting in on the router.

Correct Answer
Jennifer Halim Fri, 03/19/2010 - 15:32

I guess it really depends on what you will be using the NAT for, as there is a number of application inspection that ASA is more superior of.

For example:

You are NATing your FTP server, and ASA is configured to inspect FTP traffic so it will dynamically open a pin hole for the FTP data connection.

If you perform the same on the router, first of all, for tighter security, you would need to create access-list, and then either CBAC or ZBFW to inspect the traffic. Router main functionality is performing routing, with the above example, you have just added security feature on the router which is not very efficient since you already have ASA firewall.

Hope that helps.

Correct Answer
Kureli Sankar Fri, 03/19/2010 - 15:38

configuring policy nat, dynamic nat, nat exemption, outside nat, destination nat, static 1-1, policy static all of these can be easily done on the ASA.

I would say do the nat on the ASA and let the router do what is is betst to do which is routing.

-KS

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