Grandstream Networks GVC3200 Administration Manual page 38

It is used to configure the NAT traversal mechanism used on the device. It can be
selected from the dropdown list:
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If the outbound proxy is configured and used, it can be set to "NAT NO".
If set to "STUN" and STUN server is configured, the device will periodically send STUN
message to the SUTN server to get the public IP address of its NAT environment and
keep the NAT port open. STUN will not work if the NAT is symmetric type.
NAT Traversal
If set to "Keep-alive", the device will send the STUN packets to maintain the
connection that is first established during registration of the device. The "Keep-alive"
packets will fool the NAT device into keeping the connection open and this allows the
host server to send SIP requests directly to the registered device.
If the device needs to use OpenVPN to connect to host server, please set it to "VPN".
If the firewall and the SIP device behind the firewall are both able to use UPnP, it can
be set to "UPnP". Both parties will negotiate the port used to allow SIP packets to go
through.
If it is set to "TURN", the protocol is designed to be used as part of the ICE (Interactive
Connectivity Establishment) approach to NAT Traversal.
The default setting is "Keep-alive".
It is used to add the Proxy-Required header in the SIP message. It is used to indicate
Proxy-Require proxy-sensitive features that must be supported by the proxy. Do not configure this
parameter unless this feature is supported on the SIP server.
NAT NO
STUN
Keep-alive
uPnP
Auto
VPN
TURN
GVC3200/3202 Administration Guide
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