请教一下， Ubuntu 20.04 LTS 做路由， PPPoE IPv6 ping 不通，有什么解决方案吗？

# ifconfig Start

ppp0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1492
inet 180.171.157.54 netmask 255.255.255.255 destination 180.171.156.1
inet6 fe80::5807:13ab:aac1:f0fe prefixlen 10 scopeid 0x20<link>
inet6 240e:38f:671c:de4d:5807:13ab:aac1:f0fe prefixlen 64 scopeid 0x0<global>
ppp txqueuelen 3 (点对点协议)
RX packets 55918 bytes 57317344 (57.3 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 50056 bytes 4146272 (4.1 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

# ifconfig End

# ip -6 r Start

::1 dev lo proto kernel metric 256 pref medium
240e:38f:671c:de4d::/64 dev ppp0 proto kernel metric 256 expires 258912sec pref medium
fd00::/56 dev lan1 proto kernel metric 300 pref medium
fe80::/64 dev enp1s0 proto kernel metric 101 pref medium
fe80::/64 dev lan1 proto kernel metric 300 pref medium
fe80::/10 dev ppp0 metric 1 pref medium
fe80::/10 dev ppp0 proto kernel metric 256 pref medium
default via fe80::d2d0:4bff:fe06:eccc dev ppp0 proto ra metric 1024 expires 1512sec pref medium

# ip -6 r End