在宿舍搞了个Openwrt的软路由，但无论怎样设置都没能让其下设备有IPv6。检查发现openwrt是可以正常获取的，这说明校园网网口仅会分配一个v6地址，不具备分发的功能。而手上另一个路由器（自带nat6功能）却能正常分发（转发？）使用，这确信了openwrt开启nat6也能实现。
浏览个近10篇教程后，终于在恩山论坛找到解决方法，记录一下。
更新软件源并安装ip6tables和kmod-ipt-nat6
opkg update
opkg install ip6tables
opkg install kmod-ipt-nat6
将 IPv6 LAN 内网地址由 fd 开头变成 dd 开头
uci set network.globals.ula_prefix="$(uci get network.globals.ula_prefix | sed 's/^./d/')"
uci commit network
让DHCP服务器总是通告默认路由
uci set dhcp.lan.ra_default='1'
uci commit dhcp
创建 /etc/init.d/nat6 文件
> /etc/init.d/nat6
vi /etc/init.d/nat6
按i进入编辑模式，右键粘贴。按Esc退出编辑，执行:w和:q保存退出
脚本内容：
#!/bin/sh /etc/rc.common
# NAT6 init script for OpenWrt // Depends on package: kmod-ipt-nat6
# edited by Sad Pencil at 2020-02-09
# replace route command with ip command to solve issues on new OpenWRT
# edited by Sad Pencil at 2021-11-29
# update line WAN6_INTERFACE=$(uci get "network.$WAN6_NAME.device" || uci get "network.$WAN6_NAME.ifname")
START=55
# Options
# -------
# Use temporary addresses (IPv6 privacy extensions) for outgoing connections? Yes: 1 / No: 0
PRIVACY=1
# Maximum number of attempts before this script will stop in case no IPv6 route is available
# This limits the execution time of the IPv6 route lookup to (MAX_TRIES+1)*(MAX_TRIES/2) seconds. The default (15) equals 120 seconds.
MAX_TRIES=15
# An initial delay (in seconds) helps to avoid looking for the IPv6 network too early. Ideally, the first probe is successful.
# This would be the case if the time passed between the system log messages "Probing IPv6 route" and "Setting up NAT6" is 1 second.
DELAY=5
# Logical interface name of outbound IPv6 connection
# There should be no need to modify this, unless you changed the default network interface names
# Edit by Vincent: I never changed my default network interface names, but still I have to change the WAN6_NAME to "wan" instead of "wan6"
WAN6_NAME="wan6"
# ---------------------------------------------------
# Options end here - no need to change anything below
boot() {
[ $DELAY -gt 0 ] && sleep $DELAY
WAN6_INTERFACE=$(uci get "network.$WAN6_NAME.device" || uci get "network.$WAN6_NAME.ifname")
logger -t NAT6 "Probing IPv6 route"
PROBE=0
COUNT=1
while [ $PROBE -eq 0 ]
do
if [ $COUNT -gt $MAX_TRIES ]
then
logger -t NAT6 "Fatal error: No IPv6 route found (reached retry limit)" && exit 1
fi
sleep $COUNT
COUNT=$((COUNT+1))
PROBE=$(ip -6 route | grep -i '^default.*via' | grep -i -F "dev $WAN6_INTERFACE" | grep -i -o 'via.*' | wc -l)
done
logger -t NAT6 "Setting up NAT6"
if [ -z "$WAN6_INTERFACE" ] || [ ! -e "/sys/class/net/$WAN6_INTERFACE/" ] ; then
logger -t NAT6 "Fatal error: Lookup of $WAN6_NAME interface failed. Were the default interface names changed?" && exit 1
fi
WAN6_GATEWAY=$(ip -6 route | grep -i '^default.*via' | grep -i -F "dev $WAN6_INTERFACE" | grep -i -o 'via.*' | cut -d ' ' -f 2 | head -n 1)
if [ -z "$WAN6_GATEWAY" ] ; then
logger -t NAT6 "Fatal error: No IPv6 gateway for $WAN6_INTERFACE found" && exit 1
fi
LAN_ULA_PREFIX=$(uci get network.globals.ula_prefix)
if [ $(echo "$LAN_ULA_PREFIX" | grep -c -E "^([0-9a-fA-F]{4}):([0-9a-fA-F]{0,4}):") -ne 1 ] ; then
logger -t NAT6 "Fatal error: IPv6 ULA prefix $LAN_ULA_PREFIX seems invalid. Please verify that a prefix is set and valid." && exit 1
fi
ip6tables -t nat -I POSTROUTING -s "$LAN_ULA_PREFIX" -o "$WAN6_INTERFACE" -j MASQUERADE
if [ $? -eq 0 ] ; then
logger -t NAT6 "Added IPv6 masquerading rule to the firewall (Src: $LAN_ULA_PREFIX - Dst: $WAN6_INTERFACE)"
else
logger -t NAT6 "Fatal error: Failed to add IPv6 masquerading rule to the firewall (Src: $LAN_ULA_PREFIX - Dst: $WAN6_INTERFACE)" && exit 1
fi
ip -6 route add 2000::/3 via "$WAN6_GATEWAY" dev "$WAN6_INTERFACE"
if [ $? -eq 0 ] ; then
logger -t NAT6 "Added $WAN6_GATEWAY to routing table as gateway on $WAN6_INTERFACE for outgoing connections"
else
logger -t NAT6 "Error: Failed to add $WAN6_GATEWAY to routing table as gateway on $WAN6_INTERFACE for outgoing connections"
fi
if [ $PRIVACY -eq 1 ] ; then
echo 2 > "/proc/sys/net/ipv6/conf/$WAN6_INTERFACE/accept_ra"
if [ $? -eq 0 ] ; then
logger -t NAT6 "Accepting router advertisements on $WAN6_INTERFACE even if forwarding is enabled (required for temporary addresses)"
else
logger -t NAT6 "Error: Failed to change router advertisements accept policy on $WAN6_INTERFACE (required for temporary addresses)"
fi
echo 2 > "/proc/sys/net/ipv6/conf/$WAN6_INTERFACE/use_tempaddr"
if [ $? -eq 0 ] ; then
logger -t NAT6 "Using temporary addresses for outgoing connections on interface $WAN6_INTERFACE"
else
logger -t NAT6 "Error: Failed to enable temporary addresses for outgoing connections on interface $WAN6_INTERFACE"
fi
fi
exit 0
}
让nat6脚本开机启动
chmod +x /etc/init.d/nat6
/etc/init.d/nat6 enable
修改 /etc/sysctl.conf 文件
net.ipv6.conf.default.forwarding=2
net.ipv6.conf.all.forwarding=2
net.ipv6.conf.default.accept_ra=2
net.ipv6.conf.all.accept_ra=2
在防火墙中添加自定义规则
ip6tables -t nat -I POSTROUTING -s uci get network.globals.ula_prefix -j MASQUERADE
重启防火墙，重启路由器
来源：恩山无线论坛@伤心的笔 https://www.right.com.cn/forum/forum.php?mod=viewthread&tid=2661027&highlight=nat6