Cisco 521SG Administration Guide - Page 246

Cisco SPA IP Phone Field Reference SIP Tab A Parameter Insert VIA rport Substitute VIA Addr Send Resp To Src Port STUN Enable STUN Test Enable STUN Server Description Inserts the rport parameter into the VIA header of SIP responses if the received-from IP and VIA sent-by IP values differ. Select yes or no from the drop-down menu. Defaults to no. Lets you use NAT-mapped IP:port values in the VIA header. Select yes or no from the drop-down menu. Defaults to no. Sends responses to the request source port instead of the VIA sent-by port. Select yes or no from the drop-down menu. Defaults to no. Enables the use of STUN to discover NAT mapping. Select yes or no from the drop-down menu. Defaults to no. If the STUN Enable feature is enabled and a valid STUN server is available, the SPA9000 can perform a NAT-type discovery operation when it powers on. It contacts the configured STUN server, and the result of the discovery is reported in a Warning header in all subsequent REGISTER requests. If the SPA9000 detects symmetric NAT or a symmetric firewall, NAT mapping is disabled. Defaults to no. IP address or fully-qualified domain name of the STUN server to contact for NAT mapping discovery. You can use a public STUN server or set up your own STUN server. Cisco Small Business SPA300 Series, SPA500 Series, and WIP310 IP Phone Administration Guide 245