CAX80: Modem is offline - Please check RF connection

[jdimailig]

Netgear Nighthawk AX8 (CAX80)

ISP: Comcast (Xfinity)
Hardware Version: 1.01
Firmware Version: V1.1.0.36
Cable Firmware Version: V1.02.08

Trying to get the new CAX80 up and running, replacing my C6300 modem router. Unfortunately it's having issues going through the activation process.

My old C6300 still works and I remember it had working out of the box with my Xfinity service, so a little bummed that this wasn't as seamless as I hoped. For the CAX80, the online activation through the Comcast Xfinity web interface didn't work for me, nor did activation through contacting their tech support.

All I get is "Your modem is offline. Please check the RF connection."

The upstream/downstream lights were able to turn solid white, but the online light would never stop flashing. I'm told by Netgear tech it means that it was able to get a link, but unable to get assigned an address, so the issue is probably on Comcast side.

Has anyone seen this issue? I've tried both contacting Comcast (to see if they can activate by giving them the MAC address) and Netgear (to verify if they had any insight as well) for support but there was only so far I could get with the low level of support they are able to provide. Maybe because it's the weekend, but I didn't feel very confident that the support was that great.

I'm just confused because I figure if my old modem still worked (and still does), there shouldn't be anything preventing the CAX80 from getting activated either. Unless there is some difference in signal requirements between the two modems?

I've switched back to my trusty C6300 temporarily until a solution is found. Getting an Comcast Xfinity tech to come by tomorrow but am hoping there was a way to avoid it, or at least an idea of what the issue is before tomorrow, cause not knowing is driving me a little crazy.

I figure if this doesn't get resolved, I'll just refund it and refrain from upgrading my internet setup for a while.

[icaruspony]

The fact that your old modem works still shows the problem.  They would have had to delete this MAC to put in the new MAC.  So unless you had them change it back in their system, your old modem would not be working.

Try http://192.168.100.1 to see if you can get into your old modem.  Post your signal strengths and signal qualities here (basically all information that is measured in db, dbm, or dbmv).

[FURRYe38]

Contact your ISP for activation help and information. Some ISPs require the ISP to activate a new modem.

Have the ISP check the signal and line quality UP to the modem. 
Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem. 
Be sure to power OFF the modem for 1 minute them back ON.

---

@jdimailig wrote:

Netgear Nighthawk AX8 (CAX80)

ISP: Comcast (Xfinity)
Hardware Version: 1.01
Firmware Version: V1.1.0.36
Cable Firmware Version: V1.02.08

Trying to get the new CAX80 up and running, replacing my C6300 modem router. Unfortunately it's having issues going through the activation process.

My old C6300 still works and I remember it had working out of the box with my Xfinity service, so a little bummed that this wasn't as seamless as I hoped. For the CAX80, the online activation through the Comcast Xfinity web interface didn't work for me, nor did activation through contacting their tech support.

All I get is "Your modem is offline. Please check the RF connection."

The upstream/downstream lights were able to turn solid white, but the online light would never stop flashing. I'm told by Netgear tech it means that it was able to get a link, but unable to get assigned an address, so the issue is probably on Comcast side.

Has anyone seen this issue? I've tried both contacting Comcast (to see if they can activate by giving them the MAC address) and Netgear (to verify if they had any insight as well) for support but there was only so far I could get with the low level of support they are able to provide. Maybe because it's the weekend, but I didn't feel very confident that the support was that great.

I'm just confused because I figure if my old modem still worked (and still does), there shouldn't be anything preventing the CAX80 from getting activated either. Unless there is some difference in signal requirements between the two modems?

I've switched back to my trusty C6300 temporarily until a solution is found. Getting an Comcast Xfinity tech to come by tomorrow but am hoping there was a way to avoid it, or at least an idea of what the issue is before tomorrow, cause not knowing is driving me a little crazy.

I figure if this doesn't get resolved, I'll just refund it and refrain from upgrading my internet setup for a while.

---

[vkdelta]

pls post DOCSIS Connection table and Event log

[jesmith602]

I am having the exact same issue with Cox in Arizona. Router loses the Internet connection 1-2X per day and I have to reboot to get it back. Cox came out and replaced my cable line just to be sure, said they are not seeing any timeouts or packet loss and the signal levels are all in range.

Is this the table you're referring to?

Cable Connection

Cancel Apply

Frequency start Value This field below allows you to modify the frequency the cable modem start with its scan during initialization and registration. Enter the new start frequency and restart the cable modem for it to take effect. Starting Frequency

Startup Procedure

Procedure Status Comment Acquire Downstream Channel 783 MHz Locked Connectivity State OK Operational Boot State OK Operational Security Enabled BPI+

Downstream Bonded Channels

Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables 1 Locked 256 QAM 1 783000000 Hz 0.6 dBmV 39.3 dB 9372 14112 2 Locked 256 QAM 33 357000000 Hz 3.2 dBmV 40.5 dB 17 0 3 Locked 256 QAM 2 789000000 Hz 0.5 dBmV 39.1 dB 1518 2839 4 Locked 256 QAM 3 795000000 Hz 0.2 dBmV 39.0 dB 57 0 5 Locked 256 QAM 4 801000000 Hz 0.0 dBmV 38.8 dB 79 0 6 Locked 256 QAM 5 807000000 Hz 0.0 dBmV 38.8 dB 91 0 7 Locked 256 QAM 6 813000000 Hz 0.0 dBmV 38.7 dB 89 0 8 Locked 256 QAM 7 819000000 Hz 0.2 dBmV 38.8 dB 94 0 9 Locked 256 QAM 8 825000000 Hz 0.2 dBmV 38.7 dB 909 1767 10 Locked 256 QAM 9 831000000 Hz 0.1 dBmV 38.6 dB 381 914 11 Locked 256 QAM 10 837000000 Hz 0.0 dBmV 38.4 dB 738 1543 12 Locked 256 QAM 11 843000000 Hz 0.2 dBmV 38.4 dB 82 0 13 Locked 256 QAM 12 849000000 Hz 0.4 dBmV 38.3 dB 130 0 14 Locked 256 QAM 13 855000000 Hz 0.4 dBmV 38.3 dB 122 0 15 Locked 256 QAM 14 861000000 Hz 0.0 dBmV 38.1 dB 141 0 16 Locked 256 QAM 15 867000000 Hz 0.0 dBmV 38.1 dB 158 0 17 Locked 256 QAM 16 873000000 Hz 0.1 dBmV 38.2 dB 136 0 18 Locked 256 QAM 34 363000000 Hz 3.1 dBmV 40.7 dB 22 0 19 Locked 256 QAM 35 369000000 Hz 2.7 dBmV 40.7 dB 52 0 20 Locked 256 QAM 36 375000000 Hz 2.6 dBmV 40.6 dB 18 0 21 Locked 256 QAM 37 381000000 Hz 2.7 dBmV 40.7 dB 23 0 22 Locked 256 QAM 38 387000000 Hz 2.7 dBmV 40.7 dB 58 0 23 Locked 256 QAM 39 393000000 Hz 2.6 dBmV 40.7 dB 644 276 24 Locked 256 QAM 40 399000000 Hz 2.2 dBmV 40.6 dB 13 0 25 Locked 256 QAM 41 405000000 Hz 2.1 dBmV 40.6 dB 12 0 26 Locked 256 QAM 42 411000000 Hz 2.1 dBmV 40.5 dB 73 0 27 Locked 256 QAM 43 417000000 Hz 2.2 dBmV 40.6 dB 53 0 28 Locked 256 QAM 44 423000000 Hz 2.3 dBmV 40.6 dB 41 0 29 Locked 256 QAM 45 429000000 Hz 2.1 dBmV 40.5 dB 73 0 30 Locked 256 QAM 46 435000000 Hz 2.0 dBmV 40.5 dB 56 0 31 Locked 256 QAM 47 441000000 Hz 2.0 dBmV 40.6 dB 173 0 32 Locked 256 QAM 48 447000000 Hz 1.9 dBmV 40.6 dB 173 0

Upstream Bonded Channels

Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power 1 Locked ATDMA 6 2560 Ksym/sec 12900000 Hz 30.5 dBmV 2 Locked ATDMA 1 5120 Ksym/sec 17700000 Hz 27.8 dBmV 3 Locked ATDMA 2 5120 Ksym/sec 24100000 Hz 29.3 dBmV 4 Locked ATDMA 3 5120 Ksym/sec 30500000 Hz 30.0 dBmV 5 Locked ATDMA 4 5120 Ksym/sec 36900000 Hz 31.0 dBmV 6 Not Locked Unknown 0 0 0 0.0 dBmV 7 Not Locked Unknown 0 0 0 0.0 dBmV 8 Not Locked Unknown 0 0 0 0.0 dBmV

Downstream OFDM Channels

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 ,1 ,2 ,3 159 300000000 Hz 7.48 dBmV 43.0 dB 1108 ~ 2987 917553354 210270956 8 2 Not Locked 0 0 0 Hz 0 dBmV 0 dB 0 ~ 4095 0 0 0

Upstream OFDMA Channels

Channel Lock Status Modulation / Profile ID Channel ID Frequency Power 1 Not Locked 0 0 0 Hz 0 dBmV 2 Not Locked 0 0 0 Hz 0 dBmV

Extended Upstream Transmit Power

Enable Extended Upstream Transmit Power

Current System Time:Fri Sep 18 12:55:27 2020

System Up Time:05:21:15

[vkdelta]

@jesmith602  Please post Event Logs  + Logs as well (two different pages.

yes, this is the table.

[jesmith602]

@vkdelta  Thank you, the log is attached. The event log was empty (is that normal?).

[vkdelta]

event log is generally never empty.

can you please post a screenshot?

[jesmith602]

Here are all 3 logs including events. Thank you.

[jesmith602]

Hi @vkdelta @plemans -- I'm now on my second CAX80, and still having frequent disconnects. Support instructed me to have Cox reprivision the MAC and perform a hard reset with these steps, but it didn't help. Any other suggestions?

• For 2.4ghz wireless network, change the channel from auto to 11.
• For 5ghz wireless network, change the channel from auto to 128.
• Uncheck the box " Enable AX band ".
• Enable "Beamforming", "MU-MIMO", "Airtime Fairness".

Thank you.

[icaruspony]

None of those suggestions will fix the problem.  It is clear where the problem is from all the uncorrectable errors on some of the frequencies.

See, over the air TV stations, radio stations, cell towers and other things are permitted to broadcast radio frequencies through the airwaves on dedicated frequencies.  Since no two devices can share the same frequencies, the FCC acts as a traffic cop to prevent collisions.

Cable companies can use the whole spectrum that is used by the broadcasts over the airways.  This is because the coax carrying all their signal is encase, mummified, inside a foil and braid shield (usually a triple or quadrupal shielding).  This is not only to prevent over the air signals from bleeding in to your cable (ingress), but also to prevent your cable from bleeding out signals into the airwaves (leakage).

If you have a coax connector that isn't perfectly crimped, the dialectic flush with the connector with the exact amount of braid folded back onto the jacket, using the specific type of snap n seal connector for the cable used (triple vs quad shield), then this will happen.  In other words, if you have Radio Shack twist on coax connectors on a do it yourself cable.

Or if your coax has a radius bend too tight.  Or if there's a nick or cut in the coax.  Or if the connectors are not sealed and water got in the line.  Or if a single filiment/hair of shielding braid was left behind and comes in contact with the center conductor, injecting airwave signals into the coax like a giant noise gathering antenna..

The point is, a lot of errors (both correctable and uncorrectable) are happening on and around certain frequencies which are no doubt seeping in from a TV, radio, cell or otherwise station nearby.  

[icaruspony]

Also, just so you know, you basically hijacked someone else's thread.

This thread was originally by jdimailig, who was trying to install his modem, fresh, and unable to get the internet to connect for the first time.  He was getting absolutely NO INTERNET.

Then you said you were having "the exact same problem" which was disconnecting off and on daily.  Disconnecting is not the "exact same problem" as not being able to get your modem registered and signed up for internet.

That would be like if you said "my car won't start" and then I say "I have the same issue, I'm getting bad gas mileage".

You both may be using the same modem, but that's where the similarity ends.  Hopefully jdimailig got his problem resolved in spite of losing his thread to another person for something totally unrelated.  But you really should have started your own thread.

[jesmith602]

@icaruspony I guarantee you it’s ultimately the same problem, I started with the same situation of problems during the activation process. This is not an isolated issue: look at al the CAX80 threads with connection problems.

[FURRYe38]

Any progress on this? Or did you give up?

---

@jdimailig wrote:

Netgear Nighthawk AX8 (CAX80)

ISP: Comcast (Xfinity)
Hardware Version: 1.01
Firmware Version: V1.1.0.36
Cable Firmware Version: V1.02.08

Trying to get the new CAX80 up and running, replacing my C6300 modem router. Unfortunately it's having issues going through the activation process.

My old C6300 still works and I remember it had working out of the box with my Xfinity service, so a little bummed that this wasn't as seamless as I hoped. For the CAX80, the online activation through the Comcast Xfinity web interface didn't work for me, nor did activation through contacting their tech support.

All I get is "Your modem is offline. Please check the RF connection."

The upstream/downstream lights were able to turn solid white, but the online light would never stop flashing. I'm told by Netgear tech it means that it was able to get a link, but unable to get assigned an address, so the issue is probably on Comcast side.

Has anyone seen this issue? I've tried both contacting Comcast (to see if they can activate by giving them the MAC address) and Netgear (to verify if they had any insight as well) for support but there was only so far I could get with the low level of support they are able to provide. Maybe because it's the weekend, but I didn't feel very confident that the support was that great.

I'm just confused because I figure if my old modem still worked (and still does), there shouldn't be anything preventing the CAX80 from getting activated either. Unless there is some difference in signal requirements between the two modems?

I've switched back to my trusty C6300 temporarily until a solution is found. Getting an Comcast Xfinity tech to come by tomorrow but am hoping there was a way to avoid it, or at least an idea of what the issue is before tomorrow, cause not knowing is driving me a little crazy.

I figure if this doesn't get resolved, I'll just refund it and refrain from upgrading my internet setup for a while.

---

[Betachem]

Same issue here in Seattle but worse. I have woken up a couple of times and lost all my SSID’s on the device. All replaced with a version of Broadcom 2.4g or Broadcom 5g SSIDS. Called netgear they claimed they didn’t do it, called xfinity and they claimed they didn’t do it either. However this has happened twice. About once every two weeks the router goes down and I get the cannot connect to cable message and to check my rf settings. This is getting really old. This unit was supposed to work with xfinity and all I have is issues.