After re-organising the whole network lately, I wanted to get the null-route in place again for our IPv6 range. It's just nicer, than being looped around between two routers.
First barrier: It's not possible in Mikrotik. DOH !!! .. Well .. I raised a ticket with them on that.
Second barrier: I've added it like usual in the zebra daemon of quagga, by using "ipv6 route 2a02:278::/32 Null0". Well, so I thought. It actually does not work on Quagga 0.99.5, which reminds me, that I need to upgrade that box and then test it again.
Anyhow, we'll fix it via "ip" then. The command to archieve this is "ip route add 2a02:278::/32 dev lo"
Job done, all happy.