[icedchai]

I'm skeptical. How would the legacy device V4 understand the "extra bits"? How would this work on the same subnet (no router)?

[FuriouslyAdrift]

If it can't natively (by creating a new networking stack), then a router would have to re-write the packet.

Endpoint dvices should not be direct peering (security). Always go through either a passthrough inspection device or router.

[icedchai]

Endpoint devices peering directly is how things work on most small networks. What you describe would cause more problems than it solves.