Tagged and untagged sub-interfaces

To mix tagged and untagged sub-intefaces, the untagged interface needs to be configured with a VLAN ID and that VLAN ID needs to be configured as the native VLAN ID for the physical interface:

{master}[edit groups CUSTOMERS interfaces xe-101/0/2]
user@r1# show      
flexible-vlan-tagging;
native-vlan-id 1;
encapsulation flexible-ethernet-services;
unit 1 {
    vlan-id 1;
    family inet {
        address 10.0.0.1/30;
    }
}
unit 2 {
    vlan-id 2;
    family inet {
        address 10.0.0.5/30;
    }
}

user@r1# show | display set 
set groups CUSTOMERS interfaces xe-101/0/2 flexible-vlan-tagging
set groups CUSTOMERS interfaces xe-101/0/2 native-vlan-id 1
set groups CUSTOMERS interfaces xe-101/0/2 encapsulation flexible-ethernet-services
set groups CUSTOMERS interfaces xe-101/0/2 unit 1 vlan-id 1
set groups CUSTOMERS interfaces xe-101/0/2 unit 1 family inet address 10.0.0.1/30
set groups CUSTOMERS interfaces xe-101/0/2 unit 2 vlan-id 2
set groups CUSTOMERS interfaces xe-101/0/2 unit 2 family inet address 10.0.0.5/30

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