Polycom ViewStation - Manual (Page 206)

Appendix A Network Address Translation
ViewStation User Guide 190 www.polycom.com
4. Enter the NAT’s external IP address into the NAT outside
(WAN) address field.
Write down the Fixed TCP and UDP port numbers displayed on
this screen. These numbers typically are the following default
numbers:
TCP: 3230 to 3231
UDP: 3230 to 3235
5. In your NAT, reset the fixed ports from step 4 to be permanently
open, and redirect them to the IP address of your ViewStation.
6. To accept incoming calls, open and redirect port 1720 to the IP
address of your ViewStation.