isc的dhcpv6无法获取ipv6地址

[zbs168]

isc dhcpd 4.3.6版本
配置文件
subnet6 2001:xx:xxx:xxx::/64 {
range6 2001:xx:xxx:xxx::10 2001:xx:xxx:xxx::ffff;
option dhcp6.name-servers 2001:xxx:xx::131;
default-lease-time 3600;
max-lease-time 3600;
always-broadcast on;
}
当server和client在同一网段内正常获取，抓包可见4步过程，而当在h3c和华为做中继的时候，就无法获取ipv6地址，client上抓包只能看到solicit和从server返回的advertise包，client没有发出request包，求指点什么原因？
中继配置：
interface Vlanif200
ipv6 enable
ipv6 address 2001:xx:xx:xx:xxx::1/64
ipv6 nd ra prefix 2001:xx:xx:xx::/64 28800 28800
undo ipv6 nd ra halt
ipv6 nd autoconfig managed-address-flag
ipv6 nd autoconfig other-flag
dhcpv6 relay destination 2001:xx:xxx:xx:xxx