How to connect router to router - Cascading router
How to Connect Two Routers on a Home Network [Wired]
How to Setup a Second Router on Your Home Network
Connecting Two Routers Within One Network: Boosting Wi-Fi, Shared Resources
Linksys Official Support - Cascading (Connecting) a Linksys Smart Wi-Fi Router
How to connect two routers? – HMA Support
networking - Expanding wireless coverage: What are the differences between LAN to LAN and LAN to WAN when it comes to connecting two wireless routers? - Super User