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I have a cisco firewall with a /30 internet connection. There is an outside interface and an inside interface connecting to a switch where clients sit in..

All clients coming from the internal network are patted to the outside interface in order to reach the internet.

I now have a server on the internal network that i need to access form the internet. Is it true that i cannot make a static nat statement and pat into this server on port 443 using the ip-adress of the outside interface? Do i really need a /29 and more ip-adresses in order to accomplish this? If no how would i go about natting to my server? Everytime i attempt to nat asdm tells me that my nat statement would overlap with the outside interface.

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    Please provide screenshots of what you're trying to apply in ASDM. Perhaps you have the interface designations around the wrong way hence ASDM is warning about the overlap. Outside to Inside Mapping requires 'static(outside,inside)'.
    – APA
    Oct 9, 2015 at 14:45
  • PAT is really made up. The RFCs use NAPT for what some people call PAT. See RFC 2663, IP Network Address Translator (NAT) Terminology and Considerations, Section 4.1.2 Network Address Port Translation (NAPT): "NAPT extends the notion of translation one step further by also translating transport identifier (e.g., TCP and UDP port numbers, ICMP query identifiers). This allows the transport identifiers of a number of private hosts to be multiplexed into the transport identifiers of a single external address." There is more in the RFC.
    – Ron Maupin ♦
    Jan 30, 2017 at 15:50
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin ♦
    Aug 12, 2017 at 18:34

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I assume that your ASA is running with pre 8.3 IOS version...

It is similar to configuring global nat using IP in ASA where we cannot use single IP to configure multiple global nat statements and we cannot use single IP to configure multiple combinations of NAT statement..

Same applies for interface NAT also..

So you need one more IP to use for inbound connection to internal server's

You can try this for better utilization of IP's:

  1. Since it is /30 and you are configuring in your firewall outside interface directly, I assume that you are not using any dynamic protocols for subnet advertisement or receival.

  2. So you can ask service provider to configure private IP's for LAN connectivity and utilize the full /30 only to do NAT (since it is assigned to interface now, you cannot use its broadcast & unicast IP. So if you release those public IP from interface assignment, you can utilize complete /30 - 4 IP's to do NAT.. In Juniper firewall broadcast and unicast IP's can be used to do NAT by enabling point to point option though you assign /30 to interface)

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You shouldn't need extra IP's.

I have not used ASDM, but in my experience setting up a static NAT/PAT is no problem at all. Some router software can be a pain with weird or over-simplified setups for this. But I'm assuming ASDM is better than that.

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