DHCPv6[11922]: 72001011-DHCPv6 - Missing Required Option 82 & 24

@flatlander3​ I forgot to mention I'm in an apartment building so I just have the cable from the wall to the modem so there's nothing I can really change on that end. I currently have the Xfinity Gateway Modem model TG4482A. And yes, it's usually 15-30 seconds or less of what you described. I can go longer back with logs but it's all the same and system logs are empty.

@Dream32​  OK.  So you've got crippled firmware with no options.  That's too bad.  

So the question is, is your error message "normal" or not.  Welp.  Consider this one from 09:12:16 to 09:42:59:

What happens on a DHCPv6 lease rebind?  A few seconds before the rebind time, a request is generated in your gateway.  It looks at it's current IPV6 lease, and puts together the request.  Now it's a matter of closed source firmware and the script they use that we can't see -- because you are closed source.

On my gear, I can now drop the lease and request a rebind, or I can keep the current lease and request a rebind.  I found the DHCPv6 server upstream from me to be a bit flaky, so I keep the lease.  You don't have the option.  On a "normal" network where everything is working fine, it wouldn't matter.  This all takes place in much less than a second usually, and is not even perceptible in human time (or even TCP packet lifetime time). 

So you've probably dropped the lease (speculation, we can't see it), the server doesn't respond on the 1st attempt, gateway throws an error (because you've got nothing from it), and then you try again at a random interval.  Meanwhile, since you've dropped the lease, the internal LAN clients have no IPV6 gateway -- that's your stall.  You did this at 09:12:16.  Now you did end up picking up a lease because it must have succeeded sometime between 09:12:17 to 09:12:59.  Now you are good for another 1/2 hour -- we know that because 30 minutes is the next time were we try this again.

To a client, that could look like a 42 second drop out.  You can fail over to the IPV4 address, but there's a question of if that can happen before the TTL (time to live) on a TCP/IP packet expires.  Again, unknown how the firmware works.  It may not work well.  So now your active state connection to whatever you are talking to may die after another retransmit attempt fails, and you're stalled.  You have to re-establish the connection to talk to the other end again.

How can you work around a flaky DHCPv6 server?  You can try not releasing the IPV6 lease before the rebind, but you don't have the option in your firmware, or you can disable IPV6 entirely on the gateway -- which you can't do either.  You can also script the retry and bang on the DHCPv6 server multiple times on fail in succession if the problem is it's just overloaded by everyone else (not recommended).  

I do it with bridge mode, and do the networking with a firewall.  Then I can debug and script the DHCPv6 entirely, and since they only give you a /64 prefix because they are stingy with them, and I don't care all that much because my other subnets are IPV4 only.  I can just disable IPV6 every time I see an Xfinity truck doing upgrades.  I know at that point, I'm likely to have issues when "upgrades" are going on.

Not releasing the address before the rebind sometimes doesn't work either.  Their DHCPv6 server can go dark for a long time here,sometimes, and only recently started working better.  I currently have IPV6  disabled again on the WAN -- Xfinity trucks again.  

I know this is no help at all to you, but knowing how it's supposed to work may help with an equipment selection and features you want.  I understand that cleaning up the signal is rather difficult in an apartment and it might not even help with any of this since you're in the ballpark on signal.  Especially when you have no cable room access.

I'm not sure what to suggest other than if you've got a junk PC, or buy a $60 refurb, and add a 2nd Ethernet port if it doesn't have one, OPNsense and pfSense community edition are free.  You can make a firewall.  Run Bridge Mode and handle the DHCP renew/request from Xfinity yourself, disable protocol if you want, and run your WiFi with something else ($30 WiFi access point works).  

I don't know if Xfinity can solve it either.  IPV6 has been goofy at my location for over two years and they have zero answers for me.  You can try switching gateways at the Xfinity store, but that's likely not going to work either.  

I figure I'll give it a shot, when you say $60 refurb do you mean a router in order to create the firewall, or is that something done on my PC itself? (I have no knowledge of firewall things) I do use an ethernet for my PC.

@Dream32​  Hardware requirements for pfSense are here.  The community edition is free:  https://docs.netgate.com/pfsense/en/latest/hardware/index.html

opnsense docs are here.  It's all opensource and free and provides build tools so you can even compile it yourself:  https://docs.opnsense.org/ 

Just about any 64 bit machine will do.  Intel i3 or i5 processor is plenty.  Old office desktop machines work well for this. Faster is better for really complex network setups and if you are doing a whole lot of active monitoring.  You also need something with a PCI or PCI express expansion slot to add additional network interfaces if you do not have at least two Ethernet interfaces.  Look at recommended hardware for that.  I use Intel based cards.  They are more universally supported and the BSD driver is really stable.

You can use an Ethernet WiFi router too if you want.  You have to check the manual to see if it offers any control over protocol or not.  Some do, some have extremely limited control, others have no control.  None of them are very good at logging or debugging and cost more than building something that does work.