Tag Archives: ASA nat

Cisco ASA 9.1+ Static Nat example

Below shows how to configure Static nat for a web server or some kind of application running on a internal host. Basically we are port forwarding port 80 from our public IP of 1.1.1.2 to port 80 of our internal IP at 10.1.1.2. In this example Auto Nat will be used. You could also use Manual nat, I have written another blog entry on this.  This is way different than 8.2 and below. Here we create an object and then modify the object with the Static port forward we want. I

In this example my ASA outside IP is 1.1.1.1, and I want the web server to answer on 1.1.1.2.

object network 1.1.1.2
host 1.1.1.2
exit

object network 10.1.1.2
host 10.1.1.2
nat (inside,outside) static 1.1.1.2 service tcp 80 80

Somethings to note- We could name the objects anything, I just chose to use the actual IP address. For example, you could do the command ” object network Webserver-Outside” and use that name to reference the outside IP address.

Next, if I want to allow access to 10.1.1.2 from the outside world, I will need an ACL.

access-list Outside-In permit tcp any 10.1.1.2 eq 80

access-group Outside-In in interface outside

Notice the internal IP specified in the ACL – that is there on purpose. Instead of referencing the External IP  you now reference the internal.

What if the outside address answering for my web server is the outside IP of the ASA?

No problem, just have to modify that one NAT entry. Instead of the public NAT object we use the “interface” keyword.

object network 1.1.1.2
host 1.1.1.2
exit

object network 10.1.1.2
host 10.1.1.2
nat (inside,outside) static interface service tcp 80 80