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CM1100 IPv6 Problem (Xfinity)

Hi everyone,

I replaced our C7100V with a new CM1100 yesterday. After a bit of wrangling on the phone with Comcast, it's activated and working... but only on IPv4. Firmware version after the Comcast update is V2.01.02 and I'm including the event log and connection status below. The CM1100 is plugged into our firewall (Untangle v14.1.1) with IPv6 config set to Auto (SLAAC/RA). It's pulling a class A IPv4 address (73.x.x.x/23) without issue, but IPv6 is completely blank. I've tried shutting down the firewall and restarting the CM1100, then restarting the firewall, and same result.


***** Begin Event Log Paste *****
Time Priority Description
2019-03-08, 09:22:51 Notice (6) CM-STATUS message sent. Event Type Code: 3; Chan ID: N/A; DSID: �; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=14:59:c0:77:84:88;CMTS-MAC=dc:eb:94:b5:49:5f;CM-QOS=1.1;CM-VER=3.1;
2019-03-08, 09:22:51 Warning (5) Unicast DSID PSN startup error
2019-03-08, 09:19:10 Warning (5) REG-RSP-MP Mismatch Between Calculated Value for P1.6hi Compared to CCAP Provided Value;CM-MAC=14:59:c0:77:84:88;CMTS-MAC=dc:eb:94:b5:49:5f;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Notice (6) Honoring MDD; IP provisioning mode = IPv6
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=14:59:c0:77:84:88;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2019-03-08, 09:17:57 Critical (3) Resetting the cable modem due to docsDevResetNow


***** End Event Log Paste *****

***** Begin Connection Status Paste *****
<tabindex=-1>Startup Procedure</tabindex=-1>
Procedure Status Comment
Acquire Downstream Channel 663000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security Enable BPI+
IP Provisioning Mode Honor MDD IPv6 only
<tabindex=-1>Downstream Bonded Channels</tabindex=-1>
Channel Lock Status Modulation Channel ID Frequency Power SNR / MER Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked QAM256 29 663000000 Hz 0.1 dBmV 39.3 dB 66274763 0 0
2 Locked QAM256 1 483000000 Hz 0.8 dBmV 40.0 dB 65004341 0 0
3 Locked QAM256 2 489000000 Hz 0.7 dBmV 40.2 dB 65008211 0 0
4 Locked QAM256 3 495000000 Hz 0.7 dBmV 40.1 dB 65012101 0 0
5 Locked QAM256 4 507000000 Hz 0.8 dBmV 40.0 dB 65015501 0 0
6 Locked QAM256 5 513000000 Hz 0.8 dBmV 40.1 dB 65019161 0 0
7 Locked QAM256 6 519000000 Hz 0.9 dBmV 39.9 dB 65022994 0 0
8 Locked QAM256 7 525000000 Hz 1.0 dBmV 39.9 dB 65027275 0 0
9 Locked QAM256 8 531000000 Hz 0.9 dBmV 39.7 dB 65030877 0 0
10 Locked QAM256 9 543000000 Hz 0.8 dBmV 39.8 dB 65034499 0 0
11 Locked QAM256 10 549000000 Hz 0.8 dBmV 39.8 dB 65038357 0 0
12 Locked QAM256 11 555000000 Hz 0.8 dBmV 39.9 dB 65042004 0 0
13 Locked QAM256 12 561000000 Hz 0.8 dBmV 39.8 dB 65045815 0 0
14 Locked QAM256 13 567000000 Hz 0.6 dBmV 39.8 dB 65049641 1 0
15 Locked QAM256 14 573000000 Hz 0.7 dBmV 39.7 dB 65053355 0 0
16 Locked QAM256 15 579000000 Hz 0.6 dBmV 39.8 dB 65057182 0 0
17 Locked QAM256 16 585000000 Hz 0.6 dBmV 39.8 dB 65060551 1 0
18 Locked QAM256 17 591000000 Hz 0.5 dBmV 39.5 dB 65064923 0 0
19 Locked QAM256 18 597000000 Hz 0.6 dBmV 39.6 dB 65068373 0 0
20 Locked QAM256 19 603000000 Hz 0.6 dBmV 39.5 dB 65072352 2 0
21 Locked QAM256 20 609000000 Hz 0.4 dBmV 39.5 dB 65076023 0 0
22 Locked QAM256 21 615000000 Hz 0.3 dBmV 39.4 dB 65079762 5 0
23 Locked QAM256 22 621000000 Hz 0.1 dBmV 39.2 dB 65083397 0 0
24 Locked QAM256 23 627000000 Hz 0.1 dBmV 39.4 dB 65087076 4 0
25 Locked QAM256 24 633000000 Hz 0.0 dBmV 39.3 dB 65090894 0 0
26 Locked QAM256 25 639000000 Hz -0.1 dBmV 39.2 dB 65094879 0 0
27 Locked QAM256 26 645000000 Hz -0.1 dBmV 39.0 dB 65098430 0 0
28 Locked QAM256 27 651000000 Hz -0.1 dBmV 39.1 dB 65102002 3 0
29 Locked QAM256 28 657000000 Hz -0.2 dBmV 39.2 dB 65105887 1 0
30 Locked QAM256 30 669000000 Hz 0.3 dBmV 39.4 dB 65106854 2 0
31 Locked QAM256 31 675000000 Hz 0.3 dBmV 39.3 dB 65107555 0 0
32 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0 0
<tabindex=-1>Upstream Bonded Channels</tabindex=-1>
Channel Lock Status Modulation Channel ID Frequency Power
1 Locked ATDMA 1 30100000 Hz 47.8 dBmV
2 Locked ATDMA 2 36500000 Hz 47.3 dBmV
3 Locked ATDMA 3 17300000 Hz 47.8 dBmV
4 Locked ATDMA 4 23700000 Hz 47.8 dBmV
5 Not Locked Unknown 0 0 Hz 0.0 dBmV
6 Not Locked Unknown 0 0 Hz 0.0 dBmV
7 Not Locked Unknown 0 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 Hz 0.0 dBmV
<tabindex=-1>Downstream OFDM Channels</tabindex=-1>
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier Number Range Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked 0, 255 159 722000000 Hz 1.9 dBmV 38.5 dB 1126 ~ 2969 182185399 127203422 0
2 Not Locked 0, 255 0 0 Hz -1.4 dBmV 0.0 dB 0 ~ 4095 0 0 0
<tabindex=-1>Upstream OFDMA Channels</tabindex=-1>
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power
1 Not Locked Unknown 0 0 Hz 0 dBmV
2 Not Locked Unknown 0 0 Hz 0 dBmV
Current System Time: Fri Mar 08 09:43:00 2019


***** End Connection Status Paste *****


Any ideas or tips would be appreciated. I'm also engaging Comcast to see if it's on their end, and will update here with anything I find out.


Thanks!

Message 1 of 7

Accepted Solutions
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NETGEAR Employee

Re: CM1100 IPv6 Problem (Xfinity)

CM is just a bridge modem. It is not do anything for CPE side (LAN side) Ipv6 other than just mere forwarding it.

 

Comcast does DHCPv6 for the routers and provides a delegated Prefix (PD) along with it. 

 

Not sure what firewall you are using, but most linux ones support DHCPv6 with PD. 

 

 

View solution in original post

Message 6 of 7

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Highlighted
Aspirant

Re: CM1100 IPv6 Problem (Xfinity)

Update 1: 

After working with a customer expert on the Comcast forums (not an employee), I've got some more data.  Plugging a laptop directly into the port I used for the firewall and power-cycling the CM1100 resulted in the laptop pulling an IPv6 address (2001::x) and Class A IPv4 address.  Plugged the firewall back in, power-cycled again, and it still didn't get an IPv6 address. 

 

Thought 1:  Perhaps Comcast only issues addresses to its gateways via DHCPv6 and since the firewall only supports SLAAC/RA, that's the issue?

Thought 2:  Could I take the IPv6 address the laptop pulled when I connected it directly to the CM1100, and set that as a static address on the external firewall interface?

 

Thanks, and happy Friday!

Message 2 of 7
Highlighted
Aspirant

Re: CM1100 IPv6 Problem (Xfinity)

Update 2:  Let's mark this as "solved," since the CM1100 is indeed pulling an IPv6 address.  I'll continue working the issue with Untangle, since it's likely related to an issue with DHCPv6 / Native IPv6 / stateless / PD / RA, or a block of ICMPv6 traffic.

 

Thanks!

Message 3 of 7
Highlighted
Aspirant

Re: CM1100 IPv6 Problem (Xfinity)

One final question about the CM1100 - will there ever be an  ADVANCED > Advanced Setup > IPv6 settings page for the CM1100, like with other Nighthawk products?

 

Thanks!

 

Message 4 of 7
Highlighted
Sensei

Re: CM1100 IPv6 Problem (Xfinity)

   I know little about IPv6, but ...

 

> [...] the CM1100 is indeed pulling an IPv6 address. [...]

 

   The CM1100 is a modem, not a (modem+)router.  What does it care about
IPv<Anything>? I'd expect a router, or your "our firewall (Untangle
v14.1.1)", to care about such things, but not a simple modem.

 

> One final question about the CM1100 - will there ever be an ADVANCED
> > Advanced Setup > IPv6 settings page for the CM1100, like with other
> Nighthawk products?

 

   As with _which_ "other Nighthawk products"?  Do you mean Nighthawk
(modem+)_router_ products?  I wouldn't hold my breath.

Message 5 of 7
Highlighted
NETGEAR Employee

Re: CM1100 IPv6 Problem (Xfinity)

CM is just a bridge modem. It is not do anything for CPE side (LAN side) Ipv6 other than just mere forwarding it.

 

Comcast does DHCPv6 for the routers and provides a delegated Prefix (PD) along with it. 

 

Not sure what firewall you are using, but most linux ones support DHCPv6 with PD. 

 

 

View solution in original post

Message 6 of 7
Highlighted
Aspirant

Re: CM1100 IPv6 Problem (Xfinity)


@vkdelta wrote:

Comcast does DHCPv6 for the routers and provides a delegated Prefix (PD) along with it. 

 

Not sure what firewall you are using, but most linux ones support DHCPv6 with PD. 


Thanks @vkdelta (and @antinode) for your responses.  Unfortunately, finding someone at Comcast that knows anything about IPv6 is a chore.  Tier 1 support is absolutely useless in this regard- the last one I spoke with didn't even know what DHCPv6-PD was, and could only give me the Class A IPv4 address.  An informational IPv6 screen in the Advanced tab, or perhaps adding a line for "IPv6 Prefix Delegation" under Modem Status might help the more savvy user troubleshoot.

 

I'm using Untangle NG (v14.1.1), which is apparently having some issues with IPv6 in the current release.  My options for IPv6 on the WAN side are Auto (SLAAC/RA), Static, or disabled.  I'm hoping that I can statically set the prefix delegation (it does allow for changing prefix length), then use the first available address in the range on the internal side with RA enabled.  I've got a PM off to a Comcast employee that's responded to IPv6 questions in the past- hopefully they'll be able to get me the PD info.

 

In the meantime, I'm going to dig around for an old router (I know I've got a WNDR3400v2- trying to find one with 100/1000 ports) that I can slap pfSense or WRT on to muck around with as an interim solution.  Unless you want to keep this thread going, I'm going to mark vkdelta's answer as the solution to help keep the forum clean.

 

Thanks again, and happy Monday!

Message 7 of 7