my LAN with RPi3(eth0 192.168.5.5), winPC(192.168.5.4) and a router(192.168.5.1)
they could ping each other without issue.
now I have another RPi 4, connect usb C to RPi 3 , then they got usb0 interface. set them static ip address.
so RPi4 ( usb0, 192.168.5.100 ) could ping RPi3(usb0, 192.168.5.101)
and RPi4 could ping RPi3(eth0 192.168.5.5)
but RPi4 FAIL to ping router(192.168.5.1) and winPC(192.168.5.4).
enable RPi3 IP forward
sudo sysctl -w net.ipv4.ip_forward=1
ping still fail.
could you point me, what did I miss?