I'm struggling with a simple modem + router setup and I hope you'll be able to help me. For context, I work in software development but don't have particular networking skills besides things I can pick up when talking to networking engineers.
The modem is a CBN CD8000. The router is a TP-Link Archer C7 v5 (AC1750), running OpenWrt 21.02.0 r16279-5cc0535800.
First things first: if I plug an Ethernet cable from the modem to my computer, I can access the internet (as defined by "I can ping 184.108.40.206").
Now, to add the router. I'm starting from a soft factory reset after
firstboot && reboot now. I'm adding an Ethernet cable from the modem to the WAN port of the router. The router has one blue WAN port labeled "Internet" and four orange LAN ports labeled "Ethernet", so this seems like the right thing.
I take the computer cable, unplug it from the modem and plug into the router's "Ethernet 1" LAN port.
I can now ping 192.168.1.1. I can't ping 220.127.116.11 anymore (Destination Net Unreachable). Same results if the modem is connected to one of the router's LAN ports.
Any idea why this simple modem -> router -> computer wouldn't work?
Also of note:
- if I ssh into 192.168.1.1, I can't ping 18.104.22.168 either
- if I go back to the previous setup where both the router and my computer are connected to the modem, I can ping 22.214.171.124 but not 192.168.1.1.
I found Troubleshooting Internet Connectivity. Step 1 is okay: the WAN connection of the router is connected to the modem. I checked that the Ethernet cable works.
Step 2 is checking that the LAN and WAN interfaces do not share the same IPv4. LAN has the expected 192.168.1.1/24, but WAN doesn't have an IPv4 - it uses DHCP:
I tried giving it a static IP of 192.168.2.1, to no avail.
At this point it sounds a lot like I'm just missing something obvious. Thanks for reading, and I hope you can help me!