Puzzled- Deco X20 + OpenWrt on Edgerouter = no Internet X

I came across a rather puzzling situation: I run a Wireguard server on an Edgerouter X. Currently, the Edgerouter is hardwired to one of the gigabit ports of the main TP Deco X20. Everything works fine.

However, if I were to reconfigure the setup, with the Edgerouter being between the cable modem and the Deco, the Deco cannot connect to the internet and the status LED stays red. Well, it did connect twice, but didn't last and died in about 10 minutes.

Obviously I have restarted the cable modem so that it pairs with Edgerouter. The Edgerouter is connected to the cable modem via the WAN port (eth0) and the Deco is connected to the Edgerouter via a LAN port (eth1 or 2).

To be clear, the Wireguard tunnel is not up and even if it were this is the server end, not the client.

What's even more weird is that if I connect a laptop to the same LAN port, the laptop works just fine.

How do I go about troubleshooting? What could be the possible scenarios contributing to this?

Bump. Any suggestions where to look?

I'd check Deco's IP address and configured resolvers.

Hi Stan and thanks for taking the time to respond.

The Deco is configured for DHCP and the ER provides both an IP and a list of resolvers. A laptop connected to the same LAN port works just fine. I also configured the Deco with a static IP and DNS, but the outcome is the same. Very weird.

Try setting a fixed port speed, and disable auto neg. Your could also try the Ethernet port in the deco, does it work?

Are you by any chance using some custom DNSes ? Perhaps the deco is trying to call home, but fails and shuts down.

And what does the blinking LED mean, according to the manual?

As a last resort you could sign up for clodshark (30 day free trial) , and capture the traffic, or use tcpdump.

the Deco is connected to the Edgerouter via the ethernet port; there is no other option! I also thought of looking at the speed settings of the ports, but didn't find anything in OpenWRT that allows me to setup the port; the Deco does not allow you to configure the ethernet port hardware either.

I wasn't expecting any other option, but the Deco have two ports, so I assume one of them is a LAN-port.

you can use ethtool via SSH on the OpenWRT side, to fiddle around with the ethernet port settings.

Thanks, will check out the tool. Not a big fan of CLI though...but beggars can’t be choosers.

I wonder if this was resolved