| Traditional Deployment Methods | 472. Configure and save the following settings:Parameter Description Configuration MethodStatic NAT/Type Select Manual/ManualSettings, and then configure theNAT address manually.Web user interfaceEndpointCTP20NAT Public IP Address/PublicIP AddressConfigure the NAT address forthe system manually. Web user interfaceEndpointCTP20Route Traversal Configure the route traversaltype.• Auto—NAT works only whenmaking a call to a publicaddress. NAT does not workwhen making a call to aprivate address.• Compulsion—NAT workswhatever you are making acall to a public address orprivate address.Default: Auto.Web user interface3. Apply the route traversal settings to the SIP protocol.Related tasksEnabling Static NAT Feature for SIP Protocol(SIP Account and SIP IP Call)STUNIf you want to use the VCS in the intranet to place calls to the VCS in the extranet, you can use STUN server,as well as configure ALG on the router or enable static NAT on the system.STUN is a client/server protocol, which allows the system behind a NAT to discover the NAT presencefirstly, and the mapped public IP address, and then the port number that the NAT has allocated for the UDPflows to remote parties. Those information is used to establish UDP communication between two systembehind the NATs.STUN is a client/server protocol. The system works as a STUN client, sending exploratory STUN messages tothe STUN server. After that, the STUN server uses those messages to determine the public IP address andthe port (which is used to connect the public network to the intranet), and then informs the client. For moreinformation, refer to RFC3489.Capturing packets after you enable the STUN feature, you can find that the VCS sends Binding Request tothe STUN server, and then the mapped IP address and the port are placed in the Binding Response: BindingSuccess Response MAPPED-ADDRESS: 59.61.92.59:19232
