CM1100 won't connect to routers

Question

I have a CM1100 that started having issues today. It will not connect to my router. It will, however, connect directly to a laptop.

My setup is:

ISP -> CM1100 -> Router/Firewall -> APs & Switches

But the link between the CM1100 and Router/Firewall doesn't work.

If I change things up:

ISP -> CM1100 -> Laptop

Everything works just fine.

It does not matter which port I connect to on the CM1100.

Here are my troubleshooting steps:

Power cycle the modem and Router/Firewall
Check the coax connection on the CM1100
Try both ports on the CM1100
Try different WAN ports on the Router/Firewall
Try different cables with steps 2 and 3
Connect my cellular modem to the Router/Firewall and verify that internet works on both WAN ports
Try different cables between the cellular modem and Router/Firewall
Try a new Router/Firewall on the CM1100, repeating steps 2, 3 and 4
Pick-up a modem from my ISP and verify it works with both Router/Firewalls

So, I'm at a loss as what to do next. No matter what I do, I can't connect to the CM1100 through a Router/Firewall, only directly.

Has anyone experienced this?

CrimpOn · Answer

What is the router/firewall?
Are you attempting to use port aggregation?
Which Internet Service Provider?

FURRYe38 · Answer

Make sure you use LAN Port 1 for connecting to any ethernet router.&nbsp;
Make sure you power OFF the CM modem for 30 seconds then back ON after connecting any new router to the CM modem.&nbsp;
&nbsp;
Contact the Mfr of the external router/firewall for help and information regarding there product since you tested a laptop and that works.&nbsp;

CrimpOn · Answer

Xerloq wrote:
started having issues today

The CM1100 was working correctly with the router/firewall before today?

Xerloq · Answer

I use a Firewalla Gold SE. I used a Linksys MX4300 for troubleshooting. It cannot connect to the CM100 either.

I am not using port agregation

Astound Broadband

I have tried both LAN ports multiple times with multiple cables.

The CM1100 was power cycled multiple times for 30+ seconds. I've done that with and without the router connected

I don't think it's an issue with the router as it can connect through the cellular modem.

For clarity, neither the Firewalla Gold nor the MX4300 work with the CM1100. Both work with the cellular modem. A laptop connected directly to the CM1100 works.

Xerloq · Answer

Yes, it has been working since February 2024. This morning, the Firewalla began reporting the main network interface (connected to the CM1100) was down and that it had switched to the failover cellular backup. The cellular failover has the option to direct connect with Ethernet, so I connected the cellular to the router WAN port, confirmed the link to the router and had internet access on the router.

In troubleshooting, I can see the router WAN port is connected at 2.5Gb, but that there is no activity between the router WAN port and CM1100 LAN 1.

The ISP confirms that the signal is within spec and the CM1100 successfully bonds the upstream/downstream channels and connects to the network from their side.

The ISP also "reset" the modem (their words) and assigned a new IP address. This made no difference in the connection to the router.

That's when I direct connected, to rule out the CM1100 as the issue; however the CM1100 will connect directly (on both LAN ports) but will not connect to the original or backup router I tried. It seems odd that it wouldn't work with ANY router - they can't all be bad, especially since both can connect to the cellular modem.

I also tried a new modem from the ISP - it connects to both routers as well.

I also just finished connecting my network switch directly to the modem after disconnecting all but the laptop I'd used to troubleshoot, and it works.

So the only thing that doesn't work is CM100 -> Any Router.

Forum Discussion

CM1100 won't connect to routers

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