As I discovered in this post:
You use port 0 on the switch, but really port 4 are connected.
/target/linux/ramips/dts/A5-V11.dts
&esw {
mediatek,portmap = <0x00>;
mediatek,portdisable = <0x0f>;
};
/target/linux/ramips/base-files/etc/board.d/02_network
a5-v11)
ucidef_set_interface_lan "eth0.1"
ucidef_add_switch "switch0" "6@eth0"
ucidef_add_switch_vlan "switch0" "1" "6t"
;;