NAT "inside" of IPSec VPN tunnel

We have an IPSec tunnel established with a 3rd party. They assign us an IP range for us to use on “our side”. So we have to NAT our internal IP’s to their assigned IP’s. The net effect is similar to what you need to do if both networks were using the same IP range. To avoid this situation, they actually have non-routable public IP’s that they give us and that’s what we present to them. Getting the tunnel established was easy as on the IPSEC VPN Profile, I’m able to add an additional “Local Networks” to specify the IP range they provided. But once the tunnel is established, I’m unable to NAT map those VPN “Local” IP’s to my real IP’s. In the NAT Mappings, I can set Inbound and Outbound Mappings but those force me to select one of the WAN connections to select the IP’s. I can assign those IP’s on the WAN connections but then I’m pretty sure the traffic will only NAT “outside” the tunnel and not “inside” (I did of course try and it didn’t work).

Here’s a post on how to “NAT inside the tunnel” with a Cisco ASA and here’s an article on doing it with a WatchGuard firewall where they discuss NAT’ing the real address to the “masquerade” address.

Is this possible with a Balance and if so how? My situation is a little unique in that they are assigning me IP’s to use as my local IP’s inside the tunnel but the same situation would occur if both sides has the same IP range as the Cisco and WatchGuard articles address. One other twist is that the 30 or so IP’s that I need to map are all part of my PepVPN so it’s not just the first network on the Balance but static LAN IP’s on devices in the PepVPN tunnel. So I’m not sure if the Balance will publish that IPSec VPN route to the PepVPN networks devices below or if I have to add a static route on each PepLink device to route that traffic through the PepVPN.

My other option is to add a firewall to handle the VPN tunnel to the 3rd party but this client has purchased a dedicated Internet connection just for this Balance VPN network so it would be much cleaner if the Balance could handle this.



This is a feature request on the development road map; however with the current firmware another device is required to perform the NAT.


Thanks for the quick response so I don’t keep trying to trick it out to make it work. I hate to introduce another firewall just for the NAt’ing but that’s what we’ll do to get it going and hopefully we can remote it later with an upcoming firmware release.



Hello, have should we expect ability to NAT with IPsec VPN any time soon?

This is currently under development, not in any 6.2.x releases though, but very likely it will be available in next major release, please stay tuned :slight_smile:

Hi, we have just released firmware 6.3.0 beta and in this release we have introduced IPsec NAT Policy.

We are looking forward to your feedback, to try it out, please visit the following link for more information about the beta firmware:

After upgrading to firmware 6.3.0, you can enable IPsec NAT Policy by clicking the “here” link in the Local Networks help text:

A new section will then appear in Local Networks settings, in the upper part you can define the proposed networks (that the remote IPsec gateway will see, probably the virtual NAT network), and in the lower part you can define the NAT policy, Local Network is the real network that exist on the device (e.g. LAN, VLAN, or static routes), NAT Network is the translated virtual network that you need.

Some configuration examples have been given in the Local Networks help text, if there is anything not clear, please don’t hesitate to ask and we will clean it up and push them to the final 6.3.0 GA release. Thank you so much for your patience to wait for the feature and I hope this will fit your needs :slight_smile: