Hello,   If you have identical TPLINK VR1600V and you would like to use the other one as extender do the troubleshooting below PHYSICAL SETUP from the TPLINK A (main router) connect the ethernet cable to LAN port going to TPLINK B (extender) WAN port CONFIGURATION connect your device either wifi or cable to TPLINK B. access the modem GUI http://192.168.1.1 then go to ADVANCED > LAN SETTINGS > CHANGE THE IP ADDRESS from 192.168.1.1 to 192.168.1.100 or its up to you just make sure its the default.   Normally it will reboot the modem.. Once the modem reboot, access the GUI again using the new IP. 192.168.1.100   Then go ADVANCED>NETWORK>EWAN SETTINGS> untick VLAN ID > changes the Internet Connection type to "Dynamic IP"  and then save.   Wait for couple of minutes and you should be able to access the internet on your second router via cable or wifi. ... View more