NAT Compatibility

Last published : Oct 15, 2026
To establish a direct connection between an external user device and the session host, HDX™ Direct leverages hole punching for NAT traversal and STUN to facilitate the exchange of the public IP address and port mappings for the client device and session host. This is similar to how VoIP, unified communications, and P2P solutions work.
As long as firewalls and other network components are configured to allow the UDP traffic for the STUN requests and the HDX sessions, HDX Direct for external users is expected to work. However, there are certain scenarios where the NAT types of the user and session host networks lead to an incompatible combination, thus causing HDX Direct to fail.
Related information
HDX™ Direct

Validations

You can validate the NAT type and filtering on the client and the session host by using STUNTMAN’s STUN client utility:
  1. Download the appropriate package for the target platform from stunprotocol.org, and extract the contents.
  2. Open a terminal prompt and navigate to the directory where the contents were extracted.
  3. Run the following command: .\stunclient.exe stunserver2024.stunprotocol.org --mode behavior
  4. Take note of the output.
    If the binding and behavior tests are successful, both binding test and behavior test report the success and a NAT behavior is specified:
    NAT Success
    If the tests fail, binding test and/or behavior test report the failure.
    NAT Failure
  5. Run the following command: .\stunclient.exe stunserver2024.stunprotocol.org --mode filtering
  6. Take note of the output.
See the following table to determine if HDX Direct for external users is expected to work based on the test results of both the client and session host:
Client NAT Behavior Client NAT Filtering Session Host NAT Behavior Session Host NAT Filtering Expected to work?
Endpoint Independent Mapping Any Endpoint Independent Mapping Any Yes
Endpoint Independent Mapping Endpoint Independent Filtering Address Dedependent Mapping Any Yes
Endpoint Independent Mapping Address Dependent Filtering Address Dedependent Mapping Any No
Endpoint Independent Mapping Address and Port Dependent Filtering Address Dedependent Mapping Any No
Endpoint Independent Mapping Endpoint Independent Filtering Address and Port Dedependent Mapping Endpoint Independent Filtering Yes
Endpoint Independent Mapping Address Dependent Filtering Address Dedependent Mapping Any No
Endpoint Independent Mapping Address and Port Dependent Filtering Address Dedependent Mapping Any No
Address Dependent Mapping Any Endpoint Independent Mapping Endpoint Independent Filtering Yes
Address Dependent Mapping Any Endpoint Independent Mapping Address Dependent Filtering No
Address Dependent Mapping Any Endpoint Independent Mapping Address and Port Dependent Filtering No
Address Dependent Mapping Any Address Dependent Mapping Any No
Address Dependent Mapping Any Address and Port Dependent Mapping Any No
Address and Port Dependent Mapping Any Endpoint Independent Mapping Endpoint Independent Filtering Yes
Address and Port Dependent Mapping Any Endpoint Independent Mapping Address Dependent Filtering No
Address and Port Dependent Mapping Any Endpoint Independent Mapping Address and Port Dependent Filtering No
Address and Port Dependent Mapping Any Address Dependent Mapping Any No
Address and Port Dependent Mapping Any Address and Port Dependent Mapping Any No
Fail Any Any Any No
Any Any Fail Any No
Fail Any Fail Any No