Hello. So, I decided to flash my Cudy WR3000s with OpenWRT and everything went smoothly. The only problem is that my router can't access the internet. This happened even with the stock firmware just after following the quick setup (wireless router -> DHCP -> WiFi configuration. I tried power cycling the modem and switching the cables, but no luck. My other 2 routers work fine and they are connected to the same modem. I can't figure out what's causing this 
The Cudy is connected directly to the modem with the WAN port and the LAN is connected to a laptop.
The idea was to use the Cudy wr3000s as an AP connected to my NETGEAR router running OpenWRT.
My initial guess for this is that the lan subnet is colliding with the wan/upstream (ISP modem/router)'s subnet.
Please check the output from your OpenWrt router: ifstatus wan | grep address -- if that shows 192.168.1.x, the above is indeed the problem. To fix that:
Otherwise, let's see your configs.
Please connect to your OpenWrt device using ssh and copy the output of the following commands and post it here using the "Preformatted text </> " button (red circle; this works best in the 'Markdown' composer view in the blue oval):
Remember to redact passwords, VPN keys, MAC addresses and any public IP addresses you may have:
ubus call system board
cat /etc/config/network
cat /etc/config/wireless
cat /etc/config/dhcp
cat /etc/config/firewall
EDIT: If this device is intended as an AP, you will want to either use one of the lan ports or add the wan port into the bridge. Be sure to follow the bridged ap article.
Keep in mind if AP got static IP, you need to provide gw and DNS IPs too, or the AP won't have internet access (clients will though).
WR3000S is working great an AP.
It is assumed that this unnamed Netgear main router has better performance for routing.