[samplonius]

I'm not aware of any routers that can forward IPv4 in hardware, but pass IPv6 to the control plane.

Even the discontinued Catalyst 6500, which was used (and still is) by a lot of ISPs with the SUP720 supervisor, can do native IPv6.

I think you are completely wrong about this. Routers with native IPv6 were available 15 years ago, and are already getting pulled out to be replaced by the new stuff.

The reality is that, that ISP tier 1s use either Juniper MX or Cisco ASR9000 routers. These routers have good IPv6 performance.

[jauer]

Off the top of my head, Cisco routers with the PXF chipset (7304/NSE-100) had this problem for much of their service life