Hi Neil, you are correct. You need this patch on top of BIRD 1.6 to have working ECMP for IPv6. This patch is not currently merged, and we did not get any feedback on it so far or an estimate when this will happen. As you see, it's been a few months that it lies around here, so I am not sure this is ever going to happen. If you intend to apply this patch yourself, I'd recommend to use version 2 at least (http://bird.network.cz/pipermail/bird-users/2016-February/010239.html), as it includes some fixes.
Having that said, I am aware of at least another issue related to the route scan after an ECMP export, which we fixed internally in v3. In lack of interest, we did not bother to send it upstream so far. However, I will ask Mikhail to send it tomorrow, or I will do, so that other interested folks can at least find it on the list. Greetings, Arno
