换了个老的路由器测试了一下。我拨号是在路由器拨号的。所以跟光猫应该关系不大。
新路由器和老路由器的ping结果差不多，ping内网还是ping外网结果几乎一致
我留意到老款路由器是完全不支持ipv6的。
于是我把新路由的新开一个热点，不绑ipv6只要ipv4。问题解决。
真蛋疼啊这种情况。我v6是一定要的，因为很多节点都是v6直连
我跟腾讯会议的客服反馈，她根本不知道什么是ipv4和ipv6。
要是能软件内能支持我手动选择我都不用大费周章调网两三个小时。

'''
命令行一次过版本。
目标：

•    原有 lan 保持不动：10.0.0.1
•    新建一个 5G WiFi
•    新 WiFi 走 IPv4 only
•    新网段：10.0.2.1/24

把下面整段复制执行即可。

1) 新建 v4only 接口

uci -q delete network.v4only
uci -q delete network.br_v4
uci set network.v4only='interface'
uci set network.v4only.proto='static'
uci set network.v4only.device='br-v4'
uci set network.v4only.ipaddr='10.0.2.1'
uci set network.v4only.netmask='255.255.255.0'

uci set network.br_v4='device'
uci set network.br_v4.type='bridge'
uci set network.br_v4.name='br-v4'

2) 新建 DHCP，关闭 IPv6 下发

uci -q delete dhcp.v4only
uci set dhcp.v4only='dhcp'
uci set dhcp.v4only.interface='v4only'
uci set dhcp.v4only.start='100'
uci set dhcp.v4only.limit='150'
uci set dhcp.v4only.leasetime='12h'
uci set dhcp.v4only.ra='disabled'
uci set dhcp.v4only.dhcpv6='disabled'
uci set dhcp.v4only.ndp='disabled'

可选：下发国内 DNS

uci -q delete dhcp.v4only.dhcp_option
uci add_list dhcp.v4only.dhcp_option='6,223.5.5.5'
uci add_list dhcp.v4only.dhcp_option='6,119.29.29.29'
uci add_list dhcp.v4only.dhcp_option='6,114.114.114.114'

3) 新建防火墙 zone

uci -q delete firewall.v4only
uci -q delete firewall.v4only2wan
uci -q delete firewall.v4only_dns
uci -q delete firewall.v4only_dhcp

uci set firewall.v4only='zone'
uci set firewall.v4only.name='v4only'
uci set firewall.v4only.network='v4only'
uci set firewall.v4only.input='REJECT'
uci set firewall.v4only.output='ACCEPT'
uci set firewall.v4only.forward='REJECT'
uci set firewall.v4only.masq='1'
uci set firewall.v4only.mtu_fix='1'

uci set firewall.v4only2wan='forwarding'
uci set firewall.v4only2wan.src='v4only'
uci set firewall.v4only2wan.dest='wan'

放行 DHCP / DNS 到路由器

uci set firewall.v4only_dns='rule'
uci set firewall.v4only_dns.name='Allow-v4only-DNS'
uci set firewall.v4only_dns.src='v4only'
uci set firewall.v4only_dns.dest_port='53'
uci set firewall.v4only_dns.proto='tcp udp'
uci set firewall.v4only_dns.target='ACCEPT'

uci set firewall.v4only_dhcp='rule'
uci set firewall.v4only_dhcp.name='Allow-v4only-DHCP'
uci set firewall.v4only_dhcp.src='v4only'
uci set firewall.v4only_dhcp.dest_port='67-68'
uci set firewall.v4only_dhcp.proto='udp'
uci set firewall.v4only_dhcp.target='ACCEPT'

4) 新建一个 5G WiFi（radio1）

uci add wireless wifi-iface
uci set wireless.@wifi-iface[-1].device='radio1'
uci set wireless.@wifi-iface[-1].mode='ap'
uci set wireless.@wifi-iface[-1].ssid='FU_5G_v4'
uci set wireless.@wifi-iface[-1].encryption='psk2'
uci set wireless.@wifi-iface[-1].key='你的WiFi密码'
uci set wireless.@wifi-iface[-1].network='v4only'

5) 应用

uci commit network
uci commit dhcp
uci commit firewall
uci commit wireless

/etc/init.d/network restart
/etc/init.d/dnsmasq restart
/etc/init.d/firewall restart
wifi reload

执行完后效果是：

•    原 2.4G / 5G：继续 10.0.0.x，IPv4 + IPv6
•    新 FU_5G_v4：拿 10.0.2.x，只走 IPv4

验证命令：

ip addr show br-v4
uci show wireless | grep -E "ssid|network"
uci show dhcp.v4only
uci show firewall.v4only

'''