Destination NAT/PAT clarification

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Destination NAT/PAT clarification

L2 Linker

Prior to shooting myself in the foot I want to make sure I'm on the right track.

I have an application where I'd like to take inbound connections directed at a particular port on my untrusted "outside" FW interface and redirect them to the same port on an RFC1918-addressed host on my trusted "inside" interface. That is:

OUTfirewall:47808 -> INrinkchiller:47808

I'm looking a Understanding_NAT-4.1-RevC.pdf and it seems to point to a NAT policy like this:


This doesn't make a whole lot of sense to me. Am I on the right track or hopelessly confused? 🙂


L6 Presenter


Why did you choose source translation also ? I don'th think you need that.

L6 Presenter

destination translation is for inbound traffic (out to out zone) so removing the source translation would the first step. Dest translation address object should point to your internal IP. The OUTfirewall object should also reflect the public facing IP.

Thanks! So something along the lines of this?



And finally, it just occurred to me, since I'm hiding a bunch of devices behind that same external FW IP am I asking for trouble?


The security rule is good (outside to inside) destined for public facing IP. Inside to Outside source translation with dynamic IP/Port Src Translation for outbound traffic is a typical Src. NAT rule.

That config is correct.You will open only the ports what you need, so that you can protect your devices

L1 Bithead

I`m currently testing a PA to see if we are going to replace our existing FWs

However, I`m about to throw this .. out the window.

Most likely I`m to dim to get this but I`m struggling with NAT and as far as I can see its the same scenario that McMgt presents.

I need the following:

any outside on port FTP to specific inside on port FTP

ie: IP any on port FTP to IP 192.168.something on port FTP

Can someone please explain to me how to do this in layman's terms

Have you tried ?

In your case:

First create a NAT rule:

source zone: outside

destination zone: outside

destination interface: none (could be set to the physical interface if you wish)

source address: any

destination address: outside_ip

service: any (or set TCP21 along with the portrange you have defined for passive ftp preferly)

source translator: none

destination address: inside_ip

Then create a security rule:

source zone: outside

source address: any

destination zone: inside

destination address: outside_ip

application: ftp

service: application-default (or set TCP21 along with the portrange you have defined for passive ftp)

action: allow

profile: recommended to use an IPS profile thats configured according to: critical, high, medium: block - low, information: default

options: log on session end (enable log on session start for troubleshooting)

You could also use a network range instead of outside_ip. For example outside_range if thats what you mean by "any outside"?

Thank you very much mikand!

I will have another go at this and see what I can do!

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