Linksys Official Support - Upgrading the Firmware of the Linksys RE9000
Belkin Official Support - Updating your Belkin router's firmware
that firmware's router (that we are still using today) STILL hasn't been updated in ages (an old Belkin router originally bought in 2010) : r/techsupportgore
Belkin F7D4550 Router Login and Password
Belkin Official Support - Updating my Belkin router to have the latest web-based setup page
Update Belkin Router Firmware & Resolve Issues With Firmware Update
Latest Guide to do Belkin Firmware Update - Belkin Router
Belkin Official Support - Updating your Belkin router's firmware