# Remote NAT Traversal

It is assumed that a [SIP NAP](https://prosbcdocs.telcobridges.com/configuration-details/configuration-by-web-portal-category/network-access-points-nap) or a [SIP Open NAP](https://prosbcdocs.telcobridges.com/configuration-details/configuration-by-web-portal-category/network-access-points-nap/allocating-a-sip-open-network-access-point-nap) has been created and allocated.\ <br>

### To configure a Remote Symmetric NAT Traversal

1\. Select NAPs in the Navigation Panel:

<figure><img src="https://docs.telcobridges.com/w/images/3/38/NAP_NavigationMenu.png" alt=""><figcaption></figcaption></figure>

2\. Select an existing SIP NAP in the list:

<figure><img src="https://docs.telcobridges.com/w/images/e/e2/EnableSipISipT_1.png" alt=""><figcaption></figcaption></figure>

3\. Click Network Address Translation (NAT):

<figure><img src="https://docs.telcobridges.com/w/images/thumb/f/fa/Configuring_remote_or_local_nat_traversal.jpg/500px-Configuring_remote_or_local_nat_traversal.jpg" alt=""><figcaption></figcaption></figure>

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4\. SBC/Tmedia can be configured for RTP messages traversing a remote NAT as follows:<br>

* None: Remote device is not behind a NAT or remote NAT device is SIP/RTP aware.
* Force Passive Mode: Uses IP address and port from first received RTP packet to start sending RTP packets.
* Parse Direction Attribute: Uses "Passive Mode" only when "a=direction:active" is received in the SDP.<br>

Select the appropriate method for RTP NAT Traversal.

<figure><img src="https://docs.telcobridges.com/w/images/thumb/d/d9/Selecting_remote_method_for_rtp_nat_traversal.jpg/900px-Selecting_remote_method_for_rtp_nat_traversal.jpg" alt=""><figcaption></figcaption></figure>

5\. SBC/Tmedia can be configured for [SIP messages traversing a remote NAT](https://prosbcdocs.telcobridges.com/configuration-details/configuration-by-web-portal-category/ip-network-settings/configuring-nat-traversal) as follows:<br>

* None: Remote device is not behind a NAT, or reports SIP headers (contact, via) that are directly reachable.
* Automatic NAT Traversal: Automatically detects if the device is behind a NAT. This method parses the Contact IP address of the packet and check if it corresponds to a private/reserved IP range. In that case, SIP messages will be sent to the IP/Port seen in the IP header rather than the SIP headers.
* Force Use of Public IP and Port: Uses the IP and port from the IP header of the last received SIP packet.<br>

Select the appropriate method for SIP NAT traversal.

<figure><img src="https://docs.telcobridges.com/w/images/thumb/d/db/Selecting_remote_method_for_sip_nat_traversal.jpg/900px-Selecting_remote_method_for_sip_nat_traversal.jpg" alt=""><figcaption></figcaption></figure>

6\. Click Save.