Hey! Starting from kernel 4.11 (commit beb1afac518d), IPv6 are now notified using RTA_MULTIPATH, like IPv4 routes. Those routes are not handled correctly by BIRD. We handle them correctly. This also enable to parse alien routes correctly. Route modifications is still done in the old way as for insertion/deletion, this is not helpful to optimize in those cases and for replace, IPv4 case is not optimized either. It should be possible to detect appropriate support for RTA_MULTIPATH when receiving an IPv6 route with this attribute, but I don't see how it would be helpful, so I didn't do it (simpler code this way). I did some quick tests and routes are removed/added correctly: Deleted 2001:db8:a3::/64 proto bird metric 1024 nexthop via 2001:db8:ff::5 dev vti5 weight 1 nexthop via 2001:db8:ff::7 dev vti6 weight 1 2001:db8:a3::/64 via 2001:db8:ff::7 dev vti6 proto bird metric 1024 pref medium Deleted 2001:db8:a3::/64 via 2001:db8:ff::7 dev vti6 proto bird metric 1024 pref medium 2001:db8:a3::/64 via 2001:db8:ff::5 dev vti5 proto bird metric 1024 pref medium 2001:db8:a3::/64 proto bird metric 1024 nexthop via 2001:db8:ff::7 dev vti6 weight 1 nexthop via 2001:db8:ff::5 dev vti5 weight 1 Also, alien routes are correctly parsed when next-hops are correctly ordered (I didn't check if this restriction is also present for IPv4 or if Linux is always sending IPv4 multipath routes with next-hops correctly ordered): 2001:db8:a4::/64 metric 1024 nexthop via 2001:db8:ff::5 dev vti5 weight 1 nexthop via 2001:db8:ff::7 dev vti6 weight 1 2001:db8:a4::/64 multipath [kernel1 22:30:54] * (10) via 2001:db8:ff::5 on vti5 weight 1 via 2001:db8:ff::7 on vti6 weight 1 I'll try to investigate that unless someone already knows the answer. -- Make input easy to proofread. - The Elements of Programming Style (Kernighan & Plauger)