Configure Far-End NAT Traversal (FENT)

Phone trunk configuration

You may need to enable Far-End NAT Traversal (FENT) with Genesys Cloud Voice or other solutions where the Edge is not local to the physical phones and the phones are behind a NAT.

Enabling FENT allows phone communications to traverse a NAT device that is farthest away from the Edge and near the phones. It operates in conjunction with TLS and SRTP and results in the connection ignoring  the address specified in the SDP from the phone. Instead of the connection address, it latches onto the IP address where the received authenticated SRTP packets originated. This IP address is from the public side of the phone’s NAT.  Phone registrations are also latched onto and recorded as the source IP address where the Edge received the SIP REGISTER message from instead of the SIP Contact header.

To configure FENT:

1. Click Admin.
2. Under Telephony, click Trunks.
3. Click the Phones Trunks tab.
4. From the list, select the trunk you want to configure.
5. Under the Connection Configuration section, click Transport.
6. Under TLS Settings, set the Far-End NAT Traversal switch to Enabled.
7. Click Transport again to close it.
8. Click Media.
9. Use the controls in the Preferred Codec List section to add the following codecs to the list in this order:
   • audio/opus
   • audio/PCMU
10. Click Save Phone Trunk.