802.1Q Tunneling (Q-in-Q) Configuration Example

Lessons Discussion
167

Hello Sean

When using QinQ, you are able to tunnel multiple VLANs (inner VLAN tag) with a single QinQ VLAN (outer VLAN tag).

I hope this has been helpful!

Laz

168

hi,
I build my lab with two cisco routers and 3 arista switches. I configured all of boxes as same as the example but it did not work. I captured the packets among all of the boxes and I found out that the switch 2 did not pass the arp request to router 2. the arp passes switch 1 and 3 and once it goes to sw2, it did not forward it to router 2. please help?

169

Hello Manaf

Based on your description, I donā€™t have a definitive answer for why you see this behavior. Assuming everything else is configured correctly, there seems to be a problem with the configuration on SW2 and R2 and how they exchange information. I can give you some guidelines for troubleshooting that may be helpful:

  1. Do you find that ARP requests in the opposite direction are working, or do you see a similar behavior between R1 and SW1? If theyā€™re working there, you can check to see the differences in configsā€¦
  2. The ARP broadcasts must traverse both inner and outer VLAN tags. This can be blocked at the location between SW2 and R2 if there is a native VLAN mismatch, or if R2ā€™s MAC address is in the incorrect VLAN.
  3. Are the ARP requests arriving at SW2 with both VLAN tags?
  4. Check the Ethertype being used on either end of the link (see this Cisco command reference)
  5. It could be an issue with inter-vendor operation. I donā€™t know how Arista deals with QinQ, so it may be something specific to this interoperability, which may need to be further explored.

Let us know how you get along and if we can help you any further!

I hope this has been helpful!

Laz