# Using a NAT address for a VPN endpoint

VPN traffic is protected against modifications, so there are some restrictions when NAT is applied to the encrypted traffic.

If a gateway does not have a public IP address as a VPN endpoint, you might need to configure NAT traversal.

You might also need to configure the VPN with contact addresses so that the gateways are aware of the NAT operation:

- Engines that are used as VPN Gateways in a NAT environment must have Locations and Contact Addresses defined for the endpoint interfaces involved. On Engine Clusters, CVIs must have Locations and Contact Addresses defined. If Contact Addresses have already been configured for non-VPN use, the same general configuration applies to VPN communications as well. The Forcepoint VPN Client downloads its configuration from the gateway, including any contact address configuration as needed.
- Usually, External VPN Gateways must be defined using their private IP addresses. The public IP address must be added as the Contact Address for the Location of the contacting Forcepoint Network Security Platform in the Engine/VPN role.