Troubleshooting for vonage?
Call 1-866-243-4357 for Vonage tech support.
Otherwise, if you know anything about vonage, treat the vonage
box like any other router. Preferably connect it directly to your
modem and put any other equipment behind it. If that's not
possible, try to set up QOS on the router in front of it. If you
need to use port forwarding, vonage service typically uses ports
5061, 10000 and 10050-10150 UDP.