I am not sure if I would call this a bug, but ill let you decide.
test lab all running 1.2.0-rc9
3 routers all running OSPF, l2tpv3 tunnel between the "left" and "right" router through the "middle"
middle router announces default route.
l2tpv3 local/remote ip is the loopback address
When the router is booting up it hits the l2tpv3 config section before it has started OSPF and shared routes, this makes the remote-ip of the l2tpv3 tunnel unreachable.
I know that the linux l2tp tool will not let you create a tunnel where there remote-ip is unreachable.
for example on a device with no default gateway:
sudo ip l2tp add tunnel tunnel_id 100 peer_tunnel_id 100 encap ip local 10.0.0.1 remote 10.100.100.1
RTNETLINK answers: Network is unreachable
When you have the situation where you are trying to create an l2tpv3 tunnel and the remote ip is unreachable, it fails. This seems to then delete that section of the config.
My workaround is to create a high distance(254) default gateway route that OSPF will eventually overwrite when it starts up. You could argue that it might be best practice to always turn on a default route, and I think you might be right.
This seems to be more of a bug/feature? of the linux l2tp tool itself. Maybe it makes sense to put some kind of delay in starting the l2tp section, or maybe this just needs to be documented in the wiki?