EX Series and QFX Series switches support receiving and forwarding routed or bridged Ethernet frames with 802.1Q VLAN tags.
Typically, trunk ports, which connect switches to each other, accept untagged control packets, but do not accept untagged data packets.
You can enable a trunk port to accept untagged data packets by configuring a native VLAN ID on the interface on which you want the untagged data packets to be received.
set interface-name unit logical-unit-number family ethernet-switching interface-mode trunk
set interface-name native-vlan-id number
set interface-name unit logical-unit-number family ethernet-switching vlan members native-vlan-id-number