Is the CM1100 compatible with Intel(R) Ethernet Controller I225-V?

[mostlyrobert]

I connected my Intel Ethernet Controller I225-V to my CM1100 directly. I wanted to test my ISP speeds with the 2.5GBe I225-V. It would be the best way to rule out hardware limitations with a Gigabit plan. It wouldn't DHCP or a static address to connect (or ping) the modem. The modem's LAN light is green and the computer shows an unidentified network with no internet access and a self-assigned 169 address.

How I tried to connect this ethernet adapter to the modem with DHCP and a static address:

1. power cycling
2. reboot it from Xfinity's web interface
3. factory reset with the reset button
4. a factory reset from the web interface (from an older Ubuntu 20.10 laptop that would DHCP through the modem)

After a few hours, I had to give up. My TP-Link Archer9 router and the laptop work as expected. Is there something about this LAN port that will not auto-negotiate 1000 Mbps & Full Duplex directly with the modem? I check Intel for the latest drivers. I saw some issues with an earlier version of the firmware. My issues are limited to directly connecting to the modem with this interface.

I225V Intel Gigabit Ethernet Issue Affecting Z490 Motherboards - StudioSounds Radio
Intel Network I225-V Nework issue persist even after FW upgrade - Page 2 - Intel Community

CM1100 Firmware Version  V7.01.01

Intel(R) Ethernet Controller (2) I225-V Version 1.0.2.8

Any thoughts?

[FURRYe38]

When you connect this adpater to the CM modem and reboot the modem, is this adapter the only one connected to WAN port #1. IF so, then it's possible this adapter is not compatible or there maybe something with it's drivers that isn't working right with the CM1100 modem. 

You'll only see 1000Mpbs on the adatper, if the adapter will connect. The CM1100 is only rated at 1000Mpbs and nothing higher. 

[mostlyrobert]

Yeah, the ethernet adapter is the only one connected to WAN port #1 on the modem. This motherboard has one LAN port and the "Ethernet port aggregation" feature is disabled. I had to check the manual early on to see that the second WAN port supports the LAG functionality.

[FURRYe38]

Well, if the adapter is not connecting to WAN #1 with out LAG enabled on either unit, seems like this adapter may have a problem with the CM1100. Does the adapter connect to something else like a wifi router? 

[mostlyrobert]

The ethernet adapter doesn't connect. I set the speed and duplex manually to 1 Gbps and full duplex to see if that made a difference. It never picked up an address. Every other device connects to the modem without issues. I think I need to head over to the Intel forum.

[FURRYe38]

Ya. Good Luck.