I've had a similar problem that I've now resolved and thought I'd post here for everyone's reference. I followed kevj's recommended solution of using my own router and having Comcast put the TC8305C in full bridge mode. (This was also recommended in a couple other threads.) Theoretically this worked, but I ran in to some issues with full bridge mode that I'm posting here for others' reference (and I put it in a couple other threads). I called Comcast today and was pleasantly surprised that the first CS agent I spoke with was able to switch the modem to bridge mode without any trouble. Long story short, when in bridge mode, the modem locks in to the first MAC address that asks it for a connection. For whatever reason, my new Netgear R7000 and the TC8305C did not get along while negotiating that IP address acquisition and thus was not able to retrieve an IP and get a connection to the interwebs. What I ended up doing was connecting the modem directly to my computer and then asking Comcast to send what they referred to as a "soft reset" to the modem—effectively giving it permission to hand out an IP to the next MAC address that asks for it. Once my computer negotiated the IP address (went from self-assigned, to 192.168.100.10, and then finally to a WAN IP), I confirmed I could reach the interwebs (success!). I then disconnected the modem from my computer and plugged it in to the WAN port of my Netgear. I connected to the Netgear (over WiFi) and in the "Internet Setup" advanced settings page, I changed the "Router MAC Address" from "User Default Address" to "Use This MAC Address" wherein I pasted the MAC address of my computer's ethernet port (the same one used to negotiate an IP address). I saved that setting, released/renewed the Netgear's IP address and great success! A couple notes: * It's entirely possible there is something messy between the Netgear and TC8305C's IP negotiation. If you're using a different router, you may not need to spoof the MAC address. * I had to connect to Comcast Premium support to finally get someone competent enough to help me resolve this issue (he and I came up with the MAC address spoof solution independently while working through another round of resets). It's entirely possible that typical CS will be able to send a soft reset signal if you hold their hand. (Maybe just ask them to turn off Bridge mode and then turn it back on?) * I needed to go through all of this because the TC8305C interferes with PPTP VPN traffic (as noted here: http://forums.comcast.com/t5/Home-Networking-Router-WiFi/VPN-Connection-Issue-TC8305C/td-p/1651981 and http://forums.comcast.com/t5/Home-Networking-Router-WiFi/Can-t-connect-to-VPN-using-Triple-Play-Gateway/td-p/1696057 among others). * It took at least four phone calls today to get connected to Premium support—I got disconnected three separate times and (in spite of promises to the contrary) the technicians did not call me back. The fourth time they gave me the direct number for premium support so that when I inevitably got disconnected for the fourth time, I could just call them directly. Here's the number (Comcast, feel free to censor this post and remove the number. But, please don't edit the rest of my post): 877-443-3606 (dial 1) It's a sad state of affairs when I consider today's experience as par-for-the course with beloved Comcast: I had to purchase my own hardware, spend $ on a premium support call, and spend the afternoon calling and re-calling support. (I'm cross posting this in a few other threads about VPN) Good luck.
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