ip6 bridge mode

@XfinityAbbie​ Yes, multiple restarts including factory resets. Today an Xfinity technician came and tried to help. Replaced the XB8 modem with XB7 modem and the problem is still there. Took a picture of a tcpdump dumps that shows successful request/reply when the modem is not in bridge mode and also just the requests without reply when the modem is in bridge mode. I hope someone would be able to make sense of it. 

Although at that point it is very easy for someone at Xfinity to try to reproduce. If everything works - I would be glad to have my modem replaced with one that has been verified working properly. If not - then that could be a starting point to figure out what is the problem. It may also be a regional problem if you haven't heard from anyone else. I doubt that many people care to put their modem in bridge mode and then care about ipv6.

With the modem working as intended when configured with our recommended (Non-Bridge Mode) settings, the issue you are experiencing is outside our demarcation. We recommend using the modem with our recommended settings. If you are using bridge mode, it could be due to any of the additional third-party networking equipment you may have connected to the local network. Have you ruled out the router as a potential culprit to the issue?

I get it that non-bridge mode is recommended. But is bridge mode supported even at a bare minimum with ipv6? Can you state that this is the case? I heard multiple times that it could be due to my networking equipment. I ran tcpdump on the network interface on my side and showed that your modem responds to dhcpv6 solicit message when bridge mode is off and by just turning bridge mode on your modem stops responding to dhcpv6 solicit msg. Would you say that this rules the problem being on my side? This is capturing the bytes sent over ethernet and is about the simplest thing I can do to show that you are having a problem. Same exact setup was working just four days ago without changes on my side. 

An additional clue that shows that you did something on your side is that your modem doesn't provide ipv6 network through prefix delegation anymore even when the modem has bridge mode off. Before Wednesday it was providing a 60-bit prefix network. I don't care much about this - it is just a clue that something changed on your side.

Having dealt with the Xfinity customer - I asked for the technician.

So I was hoping that the technician will come, switch the modem to bridge mode, connect an Xfinity owned device (any device, regardless of what it is - laptop, router...) and show ipv6 connectivity working. They couldn't do that. I guess they were not prepared to do it that which is fine. But at the very least I would expect someone from Xfinity to follow up next week and confirm that they tested this with such and such device and is working. And then I can get the same device and replicate the setup. Is that too much to ask?

Bridge mode should not change the modem's functionality other than disabling the built-in router function in the gateway. If this issue only happens when bridge mode is enabled is likely the router and other equipment are causing the problem. If the issue is happening whether bridge mode is enabled or disabled then that would definitely be something we would want to dig into further to see why it is happening when you are just using our gateway and have no outside equipment for your service. 

What I'm saying here is that enabling bridge mode doesn't only disable the built-in router function. It entirely prevents any ipv6 connectivity and any device (external router) from using your modem with ipv6. Isn't there some minimum level of assurance that when bridge mode is enabled there is at least one ipv6 device that is supported or at the very least tested by your QA team that it works? This is all that I'm asking. What is it? I was expecting the technician to come, switch the bridge mode on, plug some Xfinity test device and say - see, you have ipv6 connectivity so our modem works fine with at least one device - our test one. They couldn't do that.