Cisco SRP521W-K9-G1 Administration Guide - Page 130

6 Configuring Voice Configuring Voice Settings STUN Server EXT IP EXT RTP Port Min NAT Keep Alive Intvl IP address or fully-qualified domain name of the STUN server to contact for NAT mapping discovery. External IP address to substitute for the actual IP address of the SRP in all outgoing SIP messages. If 0.0.0.0 is specified, no IP address substitution is performed. If this parameter is specified, the SRP 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. NOTE: This option requires that you have (1) a static IP address from your Internet Service Provider and (2) an edge device with a symmetric NAT mechanism. If the SRP is the edge device, the second requirement is met. The default is 0.0.0.0. External port mapping number of the RTP Port Min. number. If this value is not zero, the RTP port number in all outgoing SIP messages is substituted for the corresponding port value in the external RTP port range. There is no default value. Interval between NAT-mapping keep alive messages. The default is 15. 130 Cisco SRP500 Series Services Ready Platforms Administration Guide (SRP520 Models)