> Check ip neigh output. Does the entry for your default gateway go
> STALE after those 20 minutes?
# ip -6 nei
fe80::1 dev eth0 lladdr 0c:86:10:ed:31:ca router STALE
> Also check the lifetime of any SLAAC ip addresses given in ip addr
> Do you really need to meddle with the fe80::1 route?
I had no plans to do so. I just learned during debugging that this would
reestablish IPv6 connectivity without reboot.
> Do you really
> need an explicit route for fe80::1%eth0? Will it work without?
My hosters docs (Hetzner) recommend that. They don't specify an IPv6
> Does adding a route for 2000/3 via fe80::1 dev eth0 help,
nope (just tried it)
> or is it
> really necessary to remove the default route and to re-add it?
yep, connectivity is back
> No need, an fe80::/64 IP address is only valid when an interface is
> Is the other interface connected? eth1 should not play a role here at
I had no plans to fiddle with link-local addresses, and of course eth1
settings should not matter. I just disabled IPv6 on eth1 for debugging,
and suddenly IPv6 worked >20min. Maybe coincidence rather than causality.
I'd like to learn what's going on here, thanks for your comments.