About a month ago, I signed up with Vonage.com for their Digital phone service. It communicates over port 5060/udp using my ATT cable modem for connectivity. It worked great up until last week, then I couldn't make or receive calls anymore. Using a sniffer, I determined that packets from Vonage were not making it back to my network. I contacted vonage, and they said everything was fine on their end and it was my firewall that was blocking it. They sent me a tcpdump which showed that returning packets were being blocked. However, a closer look showed that the device doing the blocking, was not the ip of my firewall, but a different device 2 hops away from me on att's network. The device is performing NAT on *only* my 5060/udp traffic, web and other traffic work fine. It's changing the source IP and the source port, and then it's not allowing returning UDP packets back through, so it breaks my connection. Why the hell would ATT be blocking my SIP traffic? Is it because they want me to buy their digital phone service and they are blocking competition? Isn't it illegal to tamper with the communication of a telephone line? Does anyone know somebody at ATT that might be able to tell me what's going on? Their tech support is clueless, and they just tell me to reboot my computer and modem. This is really pissing me off. ==================== Jay Austad Network Administrator CBS MarketWatch 612.752.1132