I've got a dual-stack (IPv4 and IPv6) set-up at a location that has two upstream connections. IPv4 stuff works just fine with static routes. Sometimes IPv6 works too. Except when it doesn't.
Software version: 5.4
[user@location] /ipv6 route> print
Flags: X - disabled, A - active, D - dynamic, C - connect, S - static, r - rip, o - ospf, b - bgp, U - unreachable
# DST-ADDRESS GATEWAY DISTANCE
0 A S ::/0 2678:dead:c007:ffff::1 1
1 S ::/0 2678:dead:beef:ffff::1 2
See, there are two default IPv6 routes. The Mikrotik 750g device can even ping the gateway IPs on both. However, the 750G upon booting/start-up DOES NOT ROUTE IPv6 PACKETS using the default routes.
IF, however, I log into the 750g and manually delete both routes and then re-add them. MAGICally, the 750G starts routing IPv6 traffic like it is supposed to. And it keeps doing so for some time. Until it breaks. (I can't predict when the box will again fail. And power cycling does nothing. Only manually removing/adding the default routes works.)
P.S. Happy World IPv6 Day!