Manual start odhcp6c cat't get address

Installing and Using OpenWrt
1

Issue:
1.Manual start odhcp6c:

/tmp # odhcp6c -s ./odhcp6c-example-script.sh -P0 -t120 eth1

--> Fail, can't get ipv6 address.

2.UCI setup wan6

uci set network.wan6=interface
uci set network.wan6.ifname="eth1"
uci set network.wan6.proto="dhcpv6"
uci commit network
ifup wan6

--> OK,

eth1      Link encap:Ethernet  HWaddr FA:7C:6A:9A:DC:47
          inet addr:192.168.1.147  Bcast:192.168.7.255  Mask:255.255.255.0
          inet6 addr: 2408:8456:3a10:7de::71e/128 Scope:Global
          inet6 addr: 2408:8456:3a10:7de:f87c:6aff:fe9a:dc47/64 Scope:Global
          inet6 addr: fe80::f87c:6aff:fe9a:dc47/64 Scope:Link

Q: Why manual start odhcp6c can't get address?

2

Check proc param.
ifup wan6:
cat /proc/sys/net/ipv6/conf/eth1/mc_forwarding --> 1

ifdown wan6:
cat /proc/sys/net/ipv6/conf/eth1/mc_forwarding --> 0

But this param mode :

ls -l mc_forwarding
-r--r--r--    1 root     root             0 Nov  8 08:10 mc_forwarding
3

Thanks very mach.