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NAT related question -

Level 2
Level 2


I have a question about using static NAT of ASA/FWSM. I'm doing some static NATs for our private servers on FWSM. I'm running out of public IP on the OUTSIDE subnet on the Firewall. We have some public IPs available on other internal subnets/VLANs that are not extended to the firewall.

I was wondering if I can use the public IP from internal subnet as for static NAT? For example, my OUTSIDE network is

I don’t want to use any IP from this network for static NAT. Instead I want to use an internal public network IP address .10 to statically NAT an internal private IP I am not using this network (120.30.41.x) on any interface of Firewall. Is it possible?

I do have routing in place. Both 120.30.41.x and 172.20.48.x are on INSIDE. I tried to do the following but it didn’t work:

Static (inside,inside) netmask

I also added alias command but it did not help either.

Alias (inside)

Does anyone have any suggestion to make it work?

thanks !!

3 Replies 3

Julio Carvajal
VIP Alumni
VIP Alumni

Hello Fawad,

Removed the commands you entered and add the following:

static (inside,outside)

With Proxy-ARP the ASA whould reply to those packets, if this still does not work, share the following

packet-tracer input outside tcp 1025 80 (If this is not a web-server then use the right service)

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Julio Carvajal
Senior Network Security and Core Specialist

The ASA outside interface I believe has its own ISP, if that ISP is not routing that network then the answer is no.

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It worked with at simple static (inside,outside). Thanks Julio !

For iternal user I had to use an alias.

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