Setting up target networking for IPv6 on ECM can be done through the host or directly on the target.

This host code sample uses a /127 prefix (only 2 addresses, 0 & 1):

$ sudo ip -6 addr add fd42::0 dev usb0
$ sudo ip -6 route add fd42::/127 dev usb0

To test the connection from the host to the target, run:

 # ping6 fd42::0

Here's the same code sample that you run on the target:

# ip -6 addr add fd42::1 dev usb0
# ip -6 route add fd42::/127 dev usb0

To test the connection from the target to the host, run

$ ping6 fd42::1

To permanently setup addresses on both sides, add the following to /etc/network/interfaces on the target:

auto usb0
iface usb0 inet6 static
    address fd42::0
    netmask 127