Cisco SPA IP Phone Field Reference
SIP Tab
Cisco Small Business SPA 300 Series, SPA 500 Series, and WIP310 IP Phone Administration Guide 231
B
 
STUN Test Enable  If the STUN Enable feature is enabled and a valid STUN 
server is available, the IP phone 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 IP phone 
detects symmetric NAT or a symmetric firewall, NAT 
mapping is disabled.
Defaults to no.
STUN Server  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.
EXT IP  External IP address to substitute for the actual IP 
address of the IP phone in all outgoing SIP messages. 
If 0.0.0.0 is specified, no IP address substitution is 
performed.
If this parameter is specified, the IP phone 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.
Defaults to blank.
EXT RTP Port Min  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.
Defaults to blank. 
NAT Keep Alive Intvl  Interval between NAT-mapping keep alive messages. 
Defaults to 15.
Parameter Description