Users may need to enable the FENT (Far-End NAT Traversal) deployment model with PureCloud Voice or other solutions where the Edge is not local to the physical phones and the phones are behind a NAT.
FENT enables features to traverse a NAT device that is farthest away from the Edge and near the phones. It operates along with TLS and SRTP and results in ignoring the connection 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 enable FENT, follow these procedures:
Follow the steps in the Configure basic settings section of the Create a SIP phone trunk article.
Follow the steps in the Configure Far-End NAT Traversal (FENT) article.