OpenWrt causing cable modem disconnects?

Hi All,

Hopefully posting this in correct category...

I have a strange issue and I am not sure how to proceed. I have a network configured as follows:

  1. Cable modem set in bridged mode
  2. wrt3200acm as router/wireless AP (ADGuard Home/firewall installed)
  3. wrt1900ac set as dumb ap with 802,11r w/ wired trunk setup between the two wrts.

Randomly 3 times an hour the modem will disconnect from ISP. I am unable to read logs on the modem (doesnt seem to store any..Rogers/canada ISP) Nothing in system log tells me why this would be happening. I recently reverted to stock openwrt image to try and eliminate bad configuration, with no success.

ISP Tech put modem in gateway mode for testing. So far, seems to have stopped the random disconnects from ISP. This is not my preferred solution as there is a NAT behind a NAT now.

Does anyone know what i should be looking at to solve this problem? Power levels in modem seem to be fine, so i am thinking its not an ISP issue, though knowing Rogers, I am not 100% convinced it isnt.

Thanks in advance.

run a continuous ping towards the IP of the cable modem, check if you see any time outs ...

Do the up and down carrier lights on the modem go out / start blinking? Cable company may be rejecting your router's MAC address and kicking the connection down. This usually resolves itself but you may need to either shut the modem completely down for some time, or call in and register your router's MAC.

Yes the carrier lights go out and then immediate start the handshaking process. Sometimes during the handshake, the lights will drop out again. Ive noticed a few times where it took the modem 3-4 times to establish connection to the ISP.

This issue has been going on for a couple months now, do you think the MAC address would be registered by now?

If you happen to be using MoCA adapters with a DOCSIS 3.1 modem, I've seen multiple daily modem de-syncs due to a compatibility issue between those technologies. (It is dependent on the ISP's particular DOCSIS 3.1 configuration whether it overlaps with MoCA frequencies. For example Comcast doesn't seem to have this problem, but Spectrum does.) In the case I experienced it was resolved by configuring the MoCA adapters to use particular frequency bands.

Interesting...I am not using MoCA but I am using Ethernet over power wiring, with the modem plugged into the filtered side of the adapter. I have tried plugging directly into the wall, with no change seen. Do you think that would have an effect?

I could see noisy power causing issues, but since changing configuration to gateway mode on the modem, the issue seems to have disappeared, which makes this even more of a mystery..

No, powerline networking won't cause this AFAIK. The MoCA/DOCSIS-3.1 thing was just a special case that someone experiencing cable modem disconnects might not think to consider.

SSH in to the router and run the following, one at a time...



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