Amazon.com: Linksys RE9000: AC3000 Tri-Band Wi-Fi Extender, Wireless Range Booster for Home, 4 Gigabit Ethernet Ports, Works with Any Wi-Fi Router (Black) : Everything Else
Linksys Official Support - How to extend your router's range with a range extender
Reuse an old router to bridge devices to your wireless network - CNET
Linksys RE9000 MU-MIMO WiFi Extender
Linksys Official Support - Configuring the Wireless Repeater mode on most Linksys Smart Wi-Fi Routers
Turn an old router into a repeater - Make:
Linksys Official Support - Configuring the Wireless Repeater mode on most Linksys Smart Wi-Fi Routers
Amazon.com: Linksys WiFi Extender, WiFi 5 Range Booster, Dual-Band Booster with High-Gain Antennas, 10,000 Sq. ft Coverage, Speeds up to (AC1200) 1.2Gbps, Uninterrupted Streaming and Gaming - RE6500HG : Electronics
Amazon.com: Cisco-Linksys Wireless-G Range Expander WRE54G : Electronics
How to use a spare router as a range booster for your Wifi Network - YouTube
Linksys Official Support - Setting up the Linksys RE9000 to Range Extender mode