Cisco 501G Administration Manual page 107

Configuring SIP, SPCP, and NAT
Network Address Translation (NAT) and Cisco IP Phones
STEP 8
STEP 9
STEP 10
Cisco SPA500 Series and WIP310 IP Phone Administration Guide
To collect information about what type of NAT your router uses click the SIP tab
and scroll to NAT Support Parameters.
SIP
Back in the tab, select yes in the
View the debug messages to determine if your network uses symmetric NAT. Look
for the Warning header in REGISTER messages, for example, Warning: 399 Spa
"Full Cone NAT detected."
Click Submit All Changes.
STUN Test Enable
drop-down box.
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