Switching

Hello.

While I completely understand the Q-in-Q, but junipers commands used in implementing it is somehow confusing for me. I have the following topology:

There are two VLANs on EX switches, vlan 123 and native vlan 9. I implemented Q-in-Q on MX 1, MX 4 and MX 2 and successfuly pinged PCs inside vlan 123 which is a tagged vlan. but was not able to ping in native vlan 9. 

Configuration on MX 1:

set interfaces ge-0/0/3 flexible-vlan-tagging
set interfaces ge-0/0/3 encapsulation flexible-ethernet-services
set interfaces ge-0/0/3 unit 300 encapsulation vlan-bridge
set interfaces ge-0/0/3 unit 300 vlan-tags outer 300
set interfaces ge-0/0/1 flexible-vlan-tagging
set interfaces ge-0/0/1 native-vlan-id 9
set interfaces ge-0/0/1 encapsulation flexible-ethernet-services
set interfaces ge-0/0/1 unit 0 encapsulation vlan-bridge
set interfaces ge-0/0/1 unit 0 vlan-id-list 123-124
set interfaces ge-0/0/1 unit 0 input-vlan-map push
set interfaces ge-0/0/1 unit 0 input-vlan-map vlan-id 300
set interfaces ge-0/0/1 unit 0 output-vlan-map pop
set bridge-domains test interface ge-0/0/3.300
set bridge-domains test interface ge-0/0/1.0

Configuration on MX 4:

set interfaces ge-0/0/1 flexible-vlan-tagging
set interfaces ge-0/0/1 encapsulation flexible-ethernet-services
set interfaces ge-0/0/1 unit 0 encapsulation vlan-bridge
set interfaces ge-0/0/1 unit 0 vlan-tags outer 300
set interfaces ge-0/0/0 flexible-vlan-tagging
set interfaces ge-0/0/0 encapsulation flexible-ethernet-services
set interfaces ge-0/0/0 unit 0 encapsulation vlan-bridge
set interfaces ge-0/0/0 unit 0 vlan-tags outer 300
set interfaces ge-0/0/1 native-vlan-id 9
set interfaces ge-0/0/0 native-vlan-id 9
 set bridge-domains test interface ge-0/0/0.0
 set bridge-domains test interface ge-0/0/1.0

Configuration on MX 2:

set interfaces ge-0/0/0 flexible-vlan-tagging
set interfaces ge-0/0/0 native-vlan-id 9
set interfaces ge-0/0/0 encapsulation flexible-ethernet-services
set interfaces ge-0/0/0 unit 0 encapsulation vlan-bridge
set interfaces ge-0/0/0 unit 0 vlan-id-list 123-124
set interfaces ge-0/0/0 unit 0 input-vlan-map push
set interfaces ge-0/0/0 unit 0 input-vlan-map vlan-id 300
set interfaces ge-0/0/0 unit 0 output-vlan-map pop
set interfaces ge-0/0/3 flexible-vlan-tagging
set interfaces ge-0/0/3 encapsulation flexible-ethernet-services
set interfaces ge-0/0/3 unit 300 encapsulation vlan-bridge
set interfaces ge-0/0/3 unit 300 vlan-tags outer 300
set bridge-domains test interface ge-0/0/3.300
set bridge-domains test interface ge-0/0/0.0

What would I missed?

regards.