root[~] $ ip -6 r s
2a01:198:200:94::/64 via :: dev sixxs  metric 256  expires 21280617sec mtu 1280 advmss 1220 hoplimit 4294967295
fe80::/64 dev eth0  metric 256  expires 21280616sec mtu 1500 advmss 1220 hoplimit 4294967295
fe80::/64 via :: dev sixxs  metric 256  expires 21280617sec mtu 1280 advmss 1220 hoplimit 4294967295
default via 2a01:198:200:94::1 dev sixxs  metric 1024  expires 21280617sec mtu 1280 advmss 1220 hoplimit 4294967295
root[~] $ ip -6 a s
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
    inet6 fe80::213:d3ff:fea9:e92f/64 scope link
       valid_lft forever preferred_lft forever
8: sixxs@NONE: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1280
    inet6 2a01:198:200:94::2/64 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::58c6:972b/128 scope link
       valid_lft forever preferred_lft forever

################
auto sixxs
iface sixxs inet6 v4tunnel
    address 2a01:198:200:94::2
    netmask 64
    endpoint 91.184.37.98
    local 88.198.151.43
    ttl 64
    up ip link set mtu 1280 dev sixxs
    up ip route add default via 2a01:198:200:94::1 dev sixxs
    down ip -6 route flush dev sixxs