Que ce soit quand ça marche ou quand c'est cassé, j'ai le même retour :
$ show ipv6 route
IPv6 Routing Table
Codes: K - kernel route, C - connected, S - static, R - RIP, O - OSPF,
IA - OSPF inter area, E1 - OSPF external type 1,
E2 - OSPF external type 2, N1 - OSPF NSSA external type 1,
N2 - OSPF NSSA external type 2, B - BGP
Timers: Uptime
IP Route Table for VRF "default"
S ::/0 [1/0] via fe80::xxxx:xxxx:xxxx:b116, eth0, 1d05h31m
C ::1/128 via ::, lo, 1d05h32m
C 2a01:xxxxxxxxxxxxx0::/64 via ::, eth1, 1d05h31m
C 2a01:xxxxxxxxxxxxx1::/64 via ::, eth1.10, 1d05h31m
C 2a01:xxxxxxxxxxxxx2::/64 via ::, eth1.20, 1d05h31m
C 2a01:xxxxxxxxxxxxx3::/64 via ::, eth0, 1d05h31m
C fe80::/64 via ::, eth1.10, 1d05h31m
$ show ipv6 route 2001:4860:4860::8888
Routing entry for ::/0
Known via "static", distance 1, metric 0, best
Last update 1d05h31m ago
* via fe80::xxxx:xxxx:xxxx:b116, eth0
Il s'agit du link-local de la Freebox.