Not applicable

Downstream light blinking green on modem(NETGEAR CM500), no internet access, logs provided

Our modem is a NETGEAR CM500 and in the morning when I woke up, the internet wasn't working. I looked at the modem and the downstream light was blinking green with the other lights solid green besides the Ethernet light which always blinks quick. I have tried resetting it, using a different coax cable, and rebooting it several of times. When I called Spectrum, they said it came through fine on their end. I later found a site NETGEAR provides which shows the logs and the status shows normal on there. This is what the website shows under the Startup Procedure:

Procedure Status Comment
Acquire Downstream Channel627000000 HzLocked
Connectivity StateOKOperational
Boot StateOKOperational
SecurityEnabledBPI+
IP Provisioning ModeIPv6 Onlyipv6Only(1)

This is what it shows under the "Downstream Bonded Channels (partial service)":

Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1LockedQAM2561627000000 Hz3 dBmV40 dB00
2LockedQAM2564645000000 Hz3.6 dBmV39.9 dB90
3Not LockedUnknown5651000000 Hz0.0 dBmV0.0 dB00
4LockedQAM2566657000000 Hz3.7 dBmV40 dB30
5LockedQAM2567663000000 Hz4.6 dBmV40.2 dB20
6LockedQAM2568669000000 Hz4.2 dBmV40.1 dB30
7LockedQAM2569675000000 Hz1.7 dBmV39.3 dB50
8LockedQAM25610681000000 Hz2.8 dBmV39.7 dB30
9LockedQAM25612693000000 Hz3.3 dBmV39.9 dB10
10LockedQAM25613699000000 Hz2.4 dBmV39.7 dB30
11LockedQAM25614705000000 Hz1.9 dBmV39.6 dB00
12LockedQAM25615711000000 Hz3.9 dBmV39.9 dB00
13LockedQAM25616717000000 Hz3.1 dBmV39.8 dB20
14LockedQAM25618729000000 Hz2.5 dBmV39.8 dB00
15LockedQAM25620741000000 Hz2.6 dBmV39.6 dB20
16LockedQAM25623759000000 Hz4.3 dBmV40 dB10

I dont know if the 3rd channel not being locked is a bad thing. Here is what is under the Upstream Bonded Channels:

Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1LockedATDMA825120 Ksym/sec24200000 Hz36.5 dBmV
2LockedTDMA812560 Ksym/sec19400000 Hz36.5 dBmV
3LockedATDMA835120 Ksym/sec30600000 Hz35.5 dBmV
4LockedATDMA845120 Ksym/sec37000000 Hz38.3 dBmV

Here is the Event Logs:

Time Priority Description
1970-1-1, 00:00:20Critical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=2c:30:33:17:53:60;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:36Critical (3)SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=2c:30:33:17:53:60;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:36Critical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=2c:30:33:17:53:60;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:47Critical (3)DHCP FAILED - Discover sent, no offer received;CM-MAC=2c:30:33:17:53:60;CMTS-MAC=00:01:5c:8b:50:68;CM-QOS=1.0;CM-VER=3.0;
2018-6-8, 00:05:15Critical (3)No Ranging Response received - T3 time-out;CM-MAC=2c:30:33:17:53:60;CMTS-MAC=00:01:5c:8b:50:68;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:21Critical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=2c:30:33:17:53:60;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:20Critical (3)SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=2c:30:33:17:53:60;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:21Critical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=2c:30:33:17:53:60;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:28Notice (6)Overriding MDD IP initialization parameters; IP provisioning mode = IPv6
2018-6-7, 20:11:03Error (4)Missing BP Configuration Setting TLV Type: 17.8;CM-MAC=2c:30:33:17:53:60;CMTS-MAC=00:01:5c:8b:50:68;CM-QOS=1.1;CM-VER=3.0;
2018-6-7, 20:11:03Error (4)Missing BP Configuration Setting TLV Type: 17.9;CM-MAC=2c:30:33:17:53:60;CMTS-MAC=00:01:5c:8b:50:68;CM-QOS=1.1;CM-VER=3.0;

When I researched this up, it said that it might lie in the coax cable from outside, but I looked out there and everything looked fine from the grounding block. Is there anything you could get from this that explains why the downstream light is blinking and the internet is down?

4 REPLIES
Established Sharer

Re: Downstream light blinking green on modem(NETGEAR CM500), no internet access, logs provided


@rinehartpa wrote:

Our modem is a NETGEAR CM500 and in the morning when I woke up, the internet wasn't working. I looked at the modem and the downstream light was blinking green with the other lights solid green besides the Ethernet light which always blinks quick. I have tried resetting it, using a different coax cable, and rebooting it several of times. When I called Spectrum, they said it came through fine on their end. I later found a site NETGEAR provides which shows the logs and the status shows normal on there. This is what the website shows under the Startup Procedure:

Procedure Status Comment
Acquire Downstream Channel627000000 HzLocked
Connectivity StateOKOperational
Boot StateOKOperational
SecurityEnabledBPI+
IP Provisioning ModeIPv6 Onlyipv6Only(1)

This is what it shows under the "Downstream Bonded Channels (partial service)":

Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1LockedQAM2561627000000 Hz3 dBmV40 dB00
2LockedQAM2564645000000 Hz3.6 dBmV39.9 dB90
3Not LockedUnknown5651000000 Hz0.0 dBmV0.0 dB00
4LockedQAM2566657000000 Hz3.7 dBmV40 dB30
5LockedQAM2567663000000 Hz4.6 dBmV40.2 dB20
6LockedQAM2568669000000 Hz4.2 dBmV40.1 dB30
7LockedQAM2569675000000 Hz1.7 dBmV39.3 dB50
8LockedQAM25610681000000 Hz2.8 dBmV39.7 dB30
9LockedQAM25612693000000 Hz3.3 dBmV39.9 dB10
10LockedQAM25613699000000 Hz2.4 dBmV39.7 dB30
11LockedQAM25614705000000 Hz1.9 dBmV39.6 dB00
12LockedQAM25615711000000 Hz3.9 dBmV39.9 dB00
13LockedQAM25616717000000 Hz3.1 dBmV39.8 dB20
14LockedQAM25618729000000 Hz2.5 dBmV39.8 dB00
15LockedQAM25620741000000 Hz2.6 dBmV39.6 dB20
16LockedQAM25623759000000 Hz4.3 dBmV40 dB10

I dont know if the 3rd channel not being locked is a bad thing. Here is what is under the Upstream Bonded Channels:

Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1LockedATDMA825120 Ksym/sec24200000 Hz36.5 dBmV
2LockedTDMA812560 Ksym/sec19400000 Hz36.5 dBmV
3LockedATDMA835120 Ksym/sec30600000 Hz35.5 dBmV
4LockedATDMA845120 Ksym/sec37000000 Hz38.3 dBmV

When I researched this up, it said that it might lie in the coax cable from outside, but I looked out there and everything looked fine from the grounding block. Is there anything you could get from this that explains why the downstream light is blinking and the internet is down?


Not too difficult - your modem cannot receive the encrypted digital signal that it expects to find on DS3 (651 MHz).  Since the modem can't 'hear' the information supposedly being sent out on channel DS3, it can't assemble complete data packets addressed to your computer. 

 

If you try to call this in to Spectrum's normal "Tier 1" tech resource, they won't know what you are talking about.  You need to have a tech come out and view those modem signal level reports.  Print out a copy before you unplug power or do a factory reset on the modem - those are Tech Support's two favorite ways to "fix your connection" that also erase the data log in your modem. 

 

The fault is most likely on Spectrum's side at the cable-to-fiber interface out along ther trunk route.  It will probably be one bad card in the shelf of eight, or a bad fiber in the bundle from the node. 

 

If you kept the manual for your modem, page 6 of the Netgear CM500 User Guide says:

 

Table 1. LED descriptions
LED
Description
Power
• Green. Power is supplied to the cable modem.
• Off. No power is supplied to the cable modem.
• Red. The cable modem is too warm and might overheat. For more information about this condition, see Use LEDs to Troubleshoot on page 24.
Downstream
• Solid amber. One downstream channel is locked.
• Blinking amber. The cable modem is scanning for a downstream channel.
• Solid green. More than one downstream channel is locked.
• Off. No downstream channel is locked.
Upstream
• Solid amber. One upstream channel is locked.
• Blinking amber. The cable modem is scanning for an upstream channel.
• Solid green. More than one upstream channel is locked.
• Off. No upstream channel is locked.
Internet
• Solid green. The cable modem is online.
• Blinking green. The cable modem is synchronizing with the cable Internet provider’s cable modem termination system (CMTS).
• Off. The cable modem is offline.
Ethernet
• Green. A powered-on device is connected to the Ethernet port at 1000 Mbps.
• Amber. A powered-on device is connected to the Ethernet port at 10/100 Mbps.
• Blinking green or amber. The Ethernet port is processing traffic.
• Off. No device is connected to the Ethernet port.

Lead Moderator

Re: Downstream light blinking green on modem(NETGEAR CM500), no internet access, logs provided

@rinehartpa Are you still experiencing issues? 

 

If the issue was resolved did you have to perform any steps? Had you spoken with support?

 

We would like to have some more detail about how things are going now. 

 

 

Regards,
Julia R.
Spectrum-Social Media Customer Care
Lead Moderator-Community Forums

Sharer

Re: Downstream light blinking green on modem(NETGEAR CM500), no internet access, logs provided

Looks like the usual signal quality issues they need to track down. Wide variance in signal strengths, and looks like it is thunking to find an alternate channel for at least one of them. A couple others might trip the process as well under more adverse conditions (summer time, higher temps and dramatic shifts in usage patterns always present challenges).

In that admin section (where you got access to the logs), there will be options for rebooting and resetting it to factory defaults. Can try the reboot button there to see if it can prod it into locking the core 16 DS channels again... but it will likely eventually do the same thing as signal quality degrades again.

It is better to use that method for the reboot because it will potentially retain most of the log, depending on how much difficulty it has latching service on the reboot. It is more of a "soft" reboot, so it just appends the existing log with the resynching entries. It is full you will likely only loose the oldest 5 or 6 entries unless it is really struggling. Pulling power for a "hard" reset will pretty much overwrite the log with a lot of entries with dates from 1970 because of the cold boot process. Resetting to manufacturer defaults is a full wipe of config and log and such... essentially refreshes the modem config completely from the head end.

Sometimes resetting to factory can make a difference though. Sometimes leads to bonding a different primary channel that improves stability. Not an absolute thing... but can be something worth trying if you find you need to reboot daily or multiple times a day. Just keep in mind you will want at least 6 hours with no forced reboots (ideally 24 hours) before a technician shows up.

Something you may want to look for concerning your coax through the house is how the cables are actually run. No hard twists or sharp turns of the cable. Anything sharper then a turn you would see around something about the size of a 2 liter bottle may compromise integrity of an RG6 cable (hopefully it is RG6 and NOT RG59) which can knacker up some frequencies in the spectrum. It is important that the structure remains within certain limits to keep resistance at 75 ohms between the conductors across the run of the cable... bend it too much and you muck things up in this regard, and an already challenged channel becomes too unstable.

Also check for signs of stress in the insulation, and all connectors are slightly more than finger tight. Not torqued up, just a touch more than finger tight. Unscrew them, make sure the copper is "shiny" and no water in there, etc. and screw them back on. Another potential issue on the resistance front... if they look bad, the tech may need to put new ends on there.
Not applicable

Re: Downstream light blinking green on modem(NETGEAR CM500), no internet access, logs provided

So later after this post when I went to plug the modem directly into the computer with an ethernet connection, it was able to load some pages at first very slowly and then a minute later it was able to load pages fine.

When the technican came I was not there, but they said they reset the router and it was working again, to where I am right now. The wifi is working again, but the DS light is still flashing on it. Since I was not there, I was not able to describe to the technician that it was something going on from outside to modem because of the DS light blinking. To karlbeckman, it is flashing green, not amber, and that was not in the manual. I still do not believe the problem has been fixed fully, it was just patched for now.