Loss of connectivity, IPv6 only (no IPv4) and DOCSIS T3/T4 errors

Perhaps IPv4 is failing when the IPv6 tunnels are updated which happened usually every 24-48hrs. Have you tried disabling IPv6? Do you need/use IPv6?

Also, do the T4 match in time to when the problem happens? If so, then it's probably not a problem with IPv6, but  a problem with the connection in general, but one that isn't effecting DHCPv6 for some reason. T4 errors are usually a problem with the downstream signal to noise ratio (SNR). Can you post your cable signal levels?

Thanks for the quick response.  One of my machines just lost IPv4 but there are no T4 events logged in the last couple hours. 

How do you disable IPv6?

Here are my SNR levels:

JiminAlpine said:
How do you disable IPv6?

Good question. It doesn't mention it anywhere in the manual, however the only manual I could find covers several different models. I found here that Netgear in general usually keeps it under ADVANCED > Advanced Setup > IPv6. Cox may have removed the ability to turn IPv6 off.

Does IPv4 fail across the entire network or just 1 computer? Do you still get a valid private IP (68.x.x.x) under "Internet Port" as shown ADVANCED > ADVANCED Home?

JiminAlpine said:
Here are my SNR levels:

Signal levels look spot on. Do you notice if they change often? Are you using any kind of coaxial signal amp or similar? See here for picture.

What may be helpful is see exactly what is going on when IPv4 fails. Next time it does, try running MiniToolBox (I use it all the time on another forum) and check off everything from "Flush DNS" to "List IP configuration" and post the results. 

Thanks again for the assist.

I see Advanced/Advanced Setup/IPv6 but no option to shut it off.

Will monitor SNR's.  I am not aware of any AMP in our coax line-up but there may be one on the street box.  I will check again in the box on house outside.

I just went down on IPv4 (IPv6 stayed up) but after a few resets am back again.  You can't do much on IPv6 except Google,  Youtube, and a few other sites I've found while mired in this problem.

I've tried flushing DNS with out success.  

I think the use of Teredo Tunneling could be a problem, all I've read says this is pretty much the least preferred method when using IPv6 over IPv4.  

Windows IP Configuration

Host Name . . . . . . . . . . . . : DESKTOP-JRV023D
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No

Ethernet adapter Ethernet:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek PCIe GBE Family Controller
Physical Address. . . . . . . . . : F4-28-53-0E-5F-E7
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IPv6 Address. . . . . . . . . . . : 2600:8801:fc04:8c00::3(Preferred)
Lease Obtained. . . . . . . . . . : Saturday, January 14, 2017 11:54:52 AM
Lease Expires . . . . . . . . . . : Saturday, January 14, 2017 1:06:36 PM
IPv6 Address. . . . . . . . . . . : 2600:8801:fc04:8c00:a446:c610:ccbd:6847(Preferred)
Temporary IPv6 Address. . . . . . : 2600:8801:fc04:8c00:b959:64fb:bd60:e15f(Preferred)
Link-local IPv6 Address . . . . . : fe80::a446:c610:ccbd:6847%4(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.0.182(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Saturday, January 14, 2017 11:56:03 AM
Lease Expires . . . . . . . . . . : Saturday, January 14, 2017 12:56:02 PM
Default Gateway . . . . . . . . . : fe80::12da:43ff:fe28:3393%4
192.168.0.1
DHCP Server . . . . . . . . . . . : 192.168.0.1
DHCPv6 IAID . . . . . . . . . . . : 83109971
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-1E-60-25-2C-00-22-15-9C-91-1C
DNS Servers . . . . . . . . . . . : 2001:578:3f::30
2001:578:3f:1::30
68.105.28.11
68.105.29.11
68.105.28.12
NetBIOS over Tcpip. . . . . . . . : Enabled

Ethernet adapter Ethernet 2:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Marvell Yukon 88E8001/8003/8010 PCI Gigabit Ethernet Controller
Physical Address. . . . . . . . . : 00-22-15-9C-A4-48
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes

Ethernet adapter Ethernet 3:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Marvell Yukon 88E8056 PCI-E Gigabit Ethernet Controller
Physical Address. . . . . . . . . : 00-22-15-9C-91-1C
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes

Tunnel adapter Local Area Connection* 2:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Microsoft Teredo Tunneling Adapter
Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes
IPv6 Address. . . . . . . . . . . : 2001:0:9d38:6abd:20c8:2c35:bb9a:f62(Preferred)
Link-local IPv6 Address . . . . . : fe80::20c8:2c35:bb9a:f62%3(Preferred)
Default Gateway . . . . . . . . . :
DHCPv6 IAID . . . . . . . . . . . : 50331648
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-1E-60-25-2C-00-22-15-9C-91-1C
NetBIOS over Tcpip. . . . . . . . : Disabled

Tunnel adapter isatap.{B6170831-A19C-441A-A73B-9679DF949F57}:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Microsoft ISATAP Adapter
Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes

I see a few things. First, IPv4 doesn't seem to be failing. It's getting a valid IP, subnet and gateway. Was this test taken when IPv4 was shown as offline? Second, you seem to have 3 NICs. Was this done to troubleshoot or do you use all 3? If so, for what?

Still looks like IPv6 is breaking DNS. Possible related to this thread.  Try disabling IPv6 on your computer. See here for the easy way, or here for the more technically correct way. If you use a different OS, please advise.

Last, I notice your DHCP leases are very short. It should be 24hr but it's only 1 hour.  Can you try setting a DHCP reservation? I don't think its causing the problem, but may help avoid it.

Lease Obtained. . . . . . . . . . : Saturday, January 14, 2017 11:56:03 AM
Lease Expires . . . . . . . . . . : Saturday, January 14, 2017 12:56:02 PM 

The more I look at this, the more it seems like a IPv6 firmware glitch related to this model. What was the original modem before getting C6300BD? Was it a similar model?

Also, you said there was no option to turn IPv6 off, but are there ANY options for it?

I had an ancient modem that always worked before upgrading to C6300BD ~6mo ago.  This modem was functioning for months until symptoms showed.   After numerous chat sessions and a Cox contractor (not their best I'm sure) visit we decided swapping the modem out with another C6300BD.  It worked flawlessly for about a week, then it all started again.

The IP info was taken when everything is up.  IPv4 is in and out now, and this page is not accessible when out.

I see no IPv6 options for the modem, but I've just been poking around different pages so there could be something there.

Will look into deactivation of IPv6, some of the MS commentary on that is a little intimidating.  

Thanks! 

Also am using an old machine that was a beast back in the day.  It came with 2 on-board ethernets, and I reccently installed a new NIC card in the PCIe thinking it would help this mess.  It didn't.

What were the symptoms with the old modem, and also what model was it? If it was a DOCSIS 2.0 modem, then it wasn't capable of IPv6, so not sure how those problems would effect a very old modem. However if you were having packet loss and loss of connection, then maybe the issue has more to do with the T3/T4 errors you are having. 

As for disabling IPv6, it's not that hard just complicated when you get to the niddy-gritty. With Windows 7 its Windows Key + R > NCPA.CPL >Double click on network adapter you are using > Uncheck "Internet Protocol Version 6" > Press OK.  The other methods are to turn it off completely(not temp disable) and a method to do it with a automatic patch fix. 

Ok thanks that was easy - I shut off IPv6.  We'll see if that helps!

I honestly don't recall why we were dropping off with the old modem.  Must be getting old myself.

This is what it look like now...

Ethernet adapter Ethernet:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek PCIe GBE Family Controller
Physical Address. . . . . . . . . : F4-28-53-0E-5F-E7
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IPv4 Address. . . . . . . . . . . : 192.168.0.4(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Saturday, January 14, 2017 3:54:58 PM
Lease Expires . . . . . . . . . . : Saturday, January 14, 2017 4:55:26 PM
Default Gateway . . . . . . . . . : 192.168.0.1
DHCP Server . . . . . . . . . . . : 192.168.0.1
DNS Servers . . . . . . . . . . . : 68.105.28.11
68.105.29.11
68.105.28.12
NetBIOS over Tcpip. . . . . . . . : Enabled

Had a few more modem errors logged recently...

That all looks good. What we need though is all that IP info when the problem is occurring. Also, noting WHEN it happens is important. I wonder if it will happen when your DHCP lease runs out at 4:55:26 PM

T4 when you have good signal suggest either a issue with the modem/gateway or a problem with the Cox service in the area. Looking at the time frame, it looks to have happened right before the last DHCP renewal. 

Also, even if you can't recall why you changed, do you remember what the old device was? Was it still a modem/router combo? If you tell me what it looked like and where you got it I can probably guess.

It just occurred to me the pig is still in my garage e-waste bin..a NETGEAR CG3000D.

Looks like I survived the lease period.  I think shutting off IPv6 may have fixed everything.

Many thanks for the help! 

Fingers crossed. If the issue comes back it might not be bad idea to PING a moderator to have a look. They might see something obvious in the area that saves us a lot of head banging.

Also, if turning off IPv6 did work, I think there is something wrong with the gateway and renewing DNS through DHCPv6. Keep that in mind if you find you ever need IPv6 on your network. Very few things require it though so you should be fine.

Lost internet again...***.   Took countless restarts and resets to come back.