This was my carelessness that did not notice the MAC address of Billion router on the packets trace which titled as VMG1302. And this is strange that one IP address (> 66.11.207.21) could be of two MAC addresses which of ZyXEL VMG1302 and Billion router. Yes, as you mentioned, > we also noticed that the WAN packets trace does not include the tftp packets neither of ZyXEL VMG1302 nor Billion router. Thus, we are confused about the test procedure and network environment. Our team now is checking this issue, but due to above reason, we are asking you for help to capture the packets and share with us the topology in parallel then we can double check it. As Ter mentioned before, connect one Cisco IP phone is OK but more than one, we just asking you for help to do the test with our VMG1302 with two or more IP phones. If the customer or you could help, it would be great appreciated. Please understanding that we have no Cisco IP phone here. Thank you.