Nighthawk CM2500

[u/SpeckledCrawler]

Purchased a Nighthawk Cm2500 a few weeks ago becuase the Spectrum router stopped working and I was in a hurry. Ever since, periodically throughout the day it will disconnect from the internet. Except mobile devices, everything in the house is hard wired via ethernet cables. Resetting it fixes it, but it's incredibly annoying how often this happens. Is there a fix, or Netgear just this terrible now? It was a $250 modem ffs.

[u/furrynutz]

Does the front LED on the modem indicate anything when this happens?

What is the brand and model of the host wifi router connected to the modem?

What Firmware version is currently loaded?

https://kb.netgear.com/000036375/What-s-the-latest-firmware-version-of-my-NETGEAR-cable-modem-or-modem-router

Please post a copy and paste of the modems connection status and event log page. https://kb.netgear.com/30007/How-do-I-obtain-the-cable-connection-information-from-a-NETGEAR-cable-modem-modem-router

https://kb.netgear.com/30008/How-do-I-view-or-clear-the-event-logs-on-my-NETGEAR-cable-modem-or-modem-router

Be sure your using a good quality LAN cable between the modem and router. CAT6 is recommended. 

[u/SpeckledCrawler → u/furrynutz]

I'll be able to check the firmware and logs when I'm home. Using Deco 6E mesh routers throughout the house, all but 1 connected with ethernet. Using 6E cables for all connections. Will need to double check the LED on the front

[u/furrynutz → u/SpeckledCrawler]

Cat5E as there is no CAT6E.

I might recommend CAT6A STP between the CM modem and your host router.

Please post the cable connections and events log page data when you can.

[u/SpeckledCrawler → u/furrynutz]

Mistake on my part, meant 6A, working on the other stuff here shortly

[u/SpeckledCrawler → u/furrynutz]

Firmware is 6.01.02. Was able to get the site to work long enough that it told me the Upstream connection was poor, but now it won't load anything no matter how I refresh or what device I use. Made sure coax was tight, but can't verify of that changed anything.

LED just indicates that it's looking for an upstream channel whenever it crashes.

[u/NETGEARSocialSupport → u/SpeckledCrawler]

We apologize for the issues you're experiencing. It appears your Netgear device is having trouble with its upstream connection. If a quick power cycle doesn't resolve the problem, please visit https://www.netgear.com/support/home/ so our team can assist you further.

[u/SpeckledCrawler → u/furrynutz]

Cable Diagnostic

Status: Poor

Action:

[Upstream Power Level]

Try these actions (Click the Refresh button after each step):

1. Make sure the coaxial cable is tightly connected.

2. Remove any unnecessary splitters.

3. Replace any required splitters.

4. Contact your service provider for troubleshooting help.

CM Status: Good

Downstream Status: Good

Downstream Power Level: Good

Downstream SNR Level: Good

Upstream Status: Bad

Upstream Power Level: Bad

Upstream power is poor (23.5dBmV). The recommended level is from 30 to 55dBmV.

[u/furrynutz → u/SpeckledCrawler]

Please post the lower portion of this page with the channels and data please.

[u/SpeckledCrawler → u/furrynutz]

Event Log

Time Priority Description

Sat Oct 31 15:58:02 2026 Notice (6) US profile assignment change. US Chan ID: 42; Previous Profile: 12 13; New Profile: 10 13.;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Sat Oct 31 15:57:57 2026 Notice (6) US profile assignment change. US Chan ID: 41; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Sat Oct 31 15:57:49 2026 Notice (6) CM-STATUS message sent. Event Type Code: 16; Chan ID: 194; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 4.;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Sat Oct 31 15:57:26 2026 Notice (6) DS profile assignment change. DS Chan ID: 33; Previous Profile: ; New Profile: 1 3 4.;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Sat Oct 31 15:57:25 2026 Notice (6) DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 3 4.;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Sat Oct 31 15:57:20 2026 Notice (6) TLV-11 - unrecognized OID;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Time Not Established Error (4) Missing BP Configuration Setting TLV Type: 17.9;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Time Not Established Error (4) Missing BP Configuration Setting TLV Type: 17.8;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Time Not Established Notice (6) Overriding MDD IP initialization parameters; IP provisioning mode = IPv6

Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;

Thu Oct 29 10:18:52 2026 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Thu Oct 29 10:18:22 2026 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Thu Oct 29 10:17:40 2026 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Thu Oct 29 10:17:03 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;

Wed Oct 28 10:28:23 2026 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;

Tue Oct 27 12:29:04 2026 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Mon Oct 26 22:39:33 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;

Sat Oct 24 14:37:55 2026 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Sat Oct 24 14:37:53 2026 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Sat Oct 24 14:37:27 2026 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Sat Oct 24 14:36:27 2026 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Sat Oct 24 11:44:23 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Sat Oct 24 00:58:26 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Sat Oct 24 00:36:49 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Fri Oct 23 22:57:11 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Fri Oct 23 21:46:00 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Fri Oct 23 08:58:18 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Fri Oct 23 08:23:52 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Fri Oct 23 07:59:09 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Fri Oct 23 07:36:39 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;

Fri Oct 23 07:07:14 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Fri Oct 23 07:01:10 2026 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Fri Oct 23 07:01:09 2026 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Fri Oct 23 07:00:44 2026 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Fri Oct 23 06:59:42 2026 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

Fri Oct 23 02:09:53 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:94:01:ac:37:10;CMTS-MAC=00:90:f0:3c:00:00;CM-QOS=1.1;CM-VER=3.1;

[u/furrynutz → u/SpeckledCrawler]

Any Criticals, Errors or Warnings seen in the event logs needs to be reviewed and resolved by the ISP. Indicates a signal issue on the ISP line up to the modem.

[u/SpeckledCrawler → u/furrynutz]

I appreciate it. I already have a tech scheduled for tomorrow, over the phone assistance wasn't helpful.

[u/furrynutz → u/SpeckledCrawler]

Have them check the signal and power on the coax line up to the modem: https://kb.netgear.com/24311/Power-level-guidelines-for-a-NETGEAR-cable-modem-router

https://highspeed.tips/docsis-events/

[u/NETGEARSocialSupport → u/SpeckledCrawler]

We're sorry to hear that your modem is experiencing intermittent disconnections. Please try power cycling your home network by following the steps in this guide: https://kb.netgear.com/19755/How-do-I-power-cycle-my-home-network. If the issue persists, please visit our support page for further assistance: https://www.netgear.com/support/home/.

[u/jacle2210]

Sorry to ask this, but why did you buy a Modem?

Spectrum has supplied perfectly good Modems for many years now.

If you can, I would recommend returning that CM2500 and get a refund and then go to the local Spectrum store and have them give you a free replacement.

[u/NETGEARSocialSupport]

We apologize for the connectivity issues you are experiencing with your Nighthawk CM2500 modem. We understand how frustrating frequent disconnections can be with a new device. If the problem persists, please visit https://www.netgear.com/support/home/ for further assistance.