@jncr Try setting the 5GHz band wireless channel to 36 and test again. Here's a story on how to set your wireless router to work with 160 MHz channel width.

@Malo87 Try setting C80 WAN static IP address outside FritzBox DHCP server range - for example 192.168.178.254 and test if that solves the issue.

@Shreyas1234 Go through this thread and check if that's a similar case as with the OP.

@ROBm23 After successful reset your username/password should be admin/admin. Connect your computer (by ethernet cable) to one of the VR400 LAN ports and open in a browser http://tplinkmodem.net or...

@Rob__ Basically you want to use a router which connects wirelessly to your main router but by wire to the RPi cluster, while keep these in different subnets, right ? Have you tried the Hotspot Mode...

@mrg9999 Here are the managed switches supporting SSH with port number from 5-10.