Configure NAT with STUN on SPA3102 Phone Adapters

Objective

Network Address Translation (NAT) allows multiple devices to access the through a router with a single public IP address assigned by an Internet Service Provider (ISP) or Internet Telephony Service Provider (ITSP). Most ITSP may support NAT mapping using a Session Border Controller (SBC) which thereby eliminates the need to manage NAT on the SPA3102. However, sometimes the ITSP network does not provide Session Border Controller functionality, so customers may not able to register with Session Initiation Protocol (SIP) providers without NAT configuration.

If you have an external static IP address and a router that can support the symmetric NAT mechanism, it is possible to use Simple Traversal of UDP through NATs (STUN) as a mechanism to discover the NAT mapping. STUN allows a client behind a NAT device (router) to find out its public address, the type of NAT it is behind, and the port associated on the Internet connection with a particular local port.

The objective of this document is to show you how to configure NAT support parameters with STUN on SPA3102 phone adapters.

Applicable Devices

• SPA3102

Configure NAT with STUN

Step 1. Use the web configuration utility to choose Admin access with Advanced settings.

Step 2. Choose Voice > Line N, where N represents the line interface number. Scroll down to the NAT Settings area.

Step 3. At the NAT Mapping Enable field, choose yes from the drop-down list to use externally mapped IP addresses and SIP/RTP ports in SIP messages. The default value is no.

Step 4. At the NAT Keep Alive Enable field, choose yes from the drop-down list to send the configured NAT keep alive message periodically. The default value is no.

Step 5. Click Submit All Changes.

Step 6. Use the web configuration utility to choose Voice > SIP. Scroll down to the NAT Support Parameters area.

Step 7. At the Handle VIA received field, choose yes from the drop-down list to process the received parameter in the VIA header. The Via header field indicates the transport used for the transaction and identifies the location where the response is to be sent. The default value is no.

Step 8. At the Handle VIA rport field, choose Yes from the drop-down list to process the rport parameter in the VIA header. The default value is no.

Step 9. At the Insert VIA received field, choose Yes from the drop-down list to insert the received parameter in the VIA header if the received-from IP address and sent-by IP address values differ. The default value is no.

Step 10. At the Insert VIA rport field, choose Yes from the drop-down list to insert the rport parameter in the VIA header if the received-from IP address and sent-by IP address values differ. The default value is no.

Step 11. At the Substitute VIA Addr field, choose Yes from the drop-down list to use NAT- mapped IP port values in the VIA header. The default value is no.

Step 12. At the Send Resp To Src Port field, choose Yes from the drop-down list to send responses to the source port instead of the VIA sent-by port. The default value is no.

Step 13. At the STUN Enable field, choose Yes from the drop-down list to enable STUN to discover NAT mapping. The default value is no.

Step 14. (Optional) At the STUN Test Enable field, choose Yes from the drop-down list to test NAT discovery every time the device powers on. You can enable STUN Test Enable only if STUN Enable is yes and a valid STUN server is available. The default value is no.

Step 15. At the STUN Server field, enter the IP address of domain name of the STUN server to contact for NAT mapping discovery.

Step 16. At the EXT IP field, enter the external IP address to substitute for the actual IP address of SPA3102 for all outgoing SIP messages. The default value is 0.0.0.0, which means the feature is disabled.

Step 17. (Optional) At the EXT RTP Port Min field, enter the external port mapping number of the Real-time Transport Protocol (RTP) Port to substitute for the corresponding port value in external RTP port range in all outgoing SIP messages. The default value is 0, which means the feature is disabled.

Step 18. At the NAT Keep Alive Intvl field, enter the interval between NAT-mapping keep alive messages in minutes. The default is 15 minutes.

Step 19. Click Submit All Changes to save the settings.