I ran into the same problem. It looks like it only happens on hosts with
IPv6 enabled.
I found a workaround for hosts where the IPv6 address is configured
statically in /etc/network/interfaces.
The workaround is to remove the 'onlink' attribute from the route, which
can be done reasonably easy by adding one "up" command to any static entry:
iface eth0 inet6 static
address 2001:0db8:85a3::7a/64
gateway 2001:0db8:85a3::1
dad-attempts 0
# dirty hack. removes 'onlink' attribute. works around #918250.
up ip -6 r change default via $IF_GATEWAY
HTH
Mike.
