Linksys SPA922 Cisco SPA9000 Voice System Administration Guide - Page 213

SPA9000 Field Reference Voice tab B Insert VIA rport Substitute VIA Addr Send Resp To Src Port STUN Enable STUN Test Enable STUN Server EXT IP 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. Default: no Lets you use NAT-mapped IP-address port values in the VIA header. Select yes or no from the drop-down menu. Default: no Sends responses to the request source port instead of the VIA sent-by port. Select yes or no from the drop-down menu. Default: no Enables the use of STUN to discover NAT mapping. Select yes or no from the drop-down menu. Default: 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 asymmetric NAT or asymmetric firewall, NAT mapping is disabled. Default: no IP address or fully-qualified domain name of the STUN server to contact for NAT mapping discovery. Default: blank External IP address to substitute for the actual IP address of the SPA9000 in all outgoing SIP messages. If 0.0.0.0 is specified, or the field is left blank, no IP address substitution is performed. NOTE You must also configure port forwarding for SIP [5060-5063] and RTP [16384-16482] when using the EXT IP field, or phone users may experience one-way audio because the RTP stream will not find its way between the two phones. If this parameter is specified, the SPA9000 assumes this IP address when generating SIP messages and SDP (if NAT Mapping is enabled for that line). However, the results of STUN and VIA received parameter processing, if available, supersede this statically configured value. Default: blank SPA9000 Voice System Administration Guide 211