@E_Smith Make sure you're using the original cable included in the router box or another quality Cat 5E/6 cable. If this persists here you can manually set the port speed to 1000mbps/full duplex...

@Aashish_AS No, you can't build OneMesh between two routers - see this FAQ - Q10/A10.

@Tapsanu Yes, the reason for the error message " The client IP address conflicts with the DHCP IP address pool. " is that the PPTP client IP address shouldn't be in the LAN subnet.

@Tapsanu Try this guide and see if it helps.

@nyonyo If you connect to WAN port (Case 2) you won't be able to set its LAN IP address in the same subnet as the main router - hence it will work as a router.

@Keeker Any would do the job. There are only DSL modem routers nowadays. Since you already have Archer c5400x router you can set the modem you've selected in bridge mode and use the Archer c5400x as...