Comment 1 for bug 1457805

But if you use VLAN tag on vrouter interface which is possible within a standard Contrail setup you loose the ability to enable dpdk feature on that compute node. Contrail is not able to configure that correctly at least not with Cisco enic (1240) nor with Intel igb (I350). Conclusion: you can't use untagged traffic to access the VLAN due to zero-vlan tag issue on Cisco UCS. You can't enable dpdk acceleration while you use VLAN taged traffic due to Contrail. Seems to be a dead end street so far.

Cisco UCS always sends untagged traffic with this dummy VLAN 0 tag, even for best effort / default QoS class traffic! Perfectly standards compliant, but highly unusual!

Juniper Contrail engineering informed about flaw via cases 2016-0310-0756 and 2016-0323-0387 (both closed), Juniper not handling the problem in JTAC.