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I was wondering if it's possible to use QinQ to send all traffic from a switch out on one interface using a QinQ tag on all frames.

What I need is to setup a wireless link between two sites using two Cisco APs (1542s). I have a lot of VLANs and using a Trunk is not possible in this scenario. I could of course just use an extra switch to connect the AP to and getting QinQ to work that way but it would be nice to not have to invest in more hardware.

Let's say I have a switch with VLANs 10, 20, 30 and 40 on both sides on and I want to connect these over the wireless link. I then want all the VLANs to be sent out on the interface where the APs are connected and add a QinQ tag on the frames before they enter the wireless link. Then ofc untag them on the other side.

Please just ask if my question is unclear. All help is appreciated!

/Rob

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  • "using a trunk is not possible" - it's always possible unless you've got overlapping VLAN IDs or other parties in control of the tags. You might need to enable 802.1Q tags on the wireless links though.
    – Zac67
    May 10 at 11:54
  • Thanks for your reply. Using a trunk is not possible as the function "VLAN transparent" needs to be disabled in the WLC for the trunking to work (according to this guide: cisco.com/c/en/us/support/docs/wireless/aironet-1560-series/…).
    – pythonnoob
    May 10 at 12:48
  • When thinking of QinQ, you'll have to make sure that the "carrier" VLAN supports sufficiently large frame sizes to accomodate full size "customer" frames (i.e. 1518 bytes of payload) There is no fragmentation nor PathMTUDiscovey at L2. The effects of having a broadcast domain with non-uniform MTU can be quite ... hilarious. The alternative, making sure that all systems connected to the given customer VLAN are aware of a nonstandard (lower) MTU, might be an even more dauting task. May 10 at 13:03
  • @pythonnoob Of course, VLAN transparent needs to be disabled to allow 802.1Q tags on the trunk. That guide describes exactly what you need. Where's the problem?
    – Zac67
    May 10 at 13:12

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