You can use the EX3300 Q-in-Q configuration presented in the attachment to configure Q-in-Q between two EX3300 devices.
Note: All devices are running Junos OS 12.3R12.4.
The goal of this PoC is to transport customer VLANs from side A to side B without having to add them inside the transit network.
First, configure the Q-in-Q switches (that is, switches that do the Q-in-Q-ing)---in this example, two EX3300 devices.
Note: Do not forget to add a license first because Q-in-Q is license based on the EX3300 device.
In the next step, configure the transit switch or switches.
This device or these devices must not be aware of any Q-in-Q or customer VLANs at all.
In this example, another EX3300 device was used just to show that no special configuration is needed.
After the setup of the Q-in-Q is completed, two switches as "client devices” were added pinging each other in VLAN 10 successfully. Of course, more customer VLANs can be added according to the needs of your network.