How-To: Configuring Q-in-Q Between Two EX3300 Devices

by on ‎01-31-2017 12:55 AM - edited on ‎10-09-2017 08:04 AM by Administrator Administrator (12,152 Views)
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.
Feb 18, 2017
Hi!!, i have a problem with qinq. The MTU is limit, how change the value of 1476byte to 1520 or more? This limit of 1476 byte is a big problem for some apps(layer 7).
Feb 22, 2017

Depending on your interface configuration, you might need to adjust the MTU value on your trunk or access ports to accommodate the 4 bytes used for the tag added by Q-in-Q tunneling.


For example, if you use the default MTU value of 1514 bytes on your access and trunk ports, you need to make one of the following adjustments:

  • Reduce the MTU on the access links by at least 4 bytes so that the frames do not exceed the MTU of the trunk link when S-VLAN tags are added.
  • Increase the MTU on the trunk link so that the link can handle the larger frame size.

We use Jumbo-MTU on all of our Trunk-Ports because the Telephone-System needs an MTU of around 7000 (odd I know).