树莓派4B + Debian10 单臂路由：光猫改桥接后PPPoE自动拨号配置

开启 ipv4 转发

# 把前边的注释删除
$ sudo vi /etc/sysctl.conf
net.ipv4.ip_forward=1
$ sudo sysctl -p

安装 pppoe 和 dnsmasq

$ sudo apt update
$ sudo apt install pppoeconf dnsmasq

网卡配置
/etc/network/interfaces.d/eth0

auto eth0
allow-hotplug eth0
iface eth0 inet static
address 10.5.6.1
netmask 255.255.255.0

auto wan
allow-hotplug wan
iface wan inet ppp
up /usr/sbin/iptables -t nat -A POSTROUTING -o wan -j MASQUERADE
up /usr/sbin/iptables -t filter -A FORWARD -p tcp -m tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
post-down /usr/sbin/iptables -t nat -D POSTROUTING -o wan -j MASQUERADE
post-down /usr/sbin/iptables -t filter -D FORWARD -p tcp -m tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu

PPPoE 配置
/etc/ppp/peers/provider

ifname wan
noipdefault
defaultroute
connect /bin/true
noauth
persist
noaccomp
usepeerdns
default-asyncmap
plugin rp-pppoe.so eth0
user "user"
lcp-echo-failure 20
lcp-echo-interval 30

PPPoE 帐号配置
/etc/ppp/pap-secrets

#       *       password
"user" * "password"

DHCP 配置
/etc/dnsmasq.conf

interface=eth0
listen-address=127.0.0.1,10.5.6.1
dhcp-range=10.5.6.100,10.5.6.200,48h

访问光猫

# 启用
$ sudo ifconfig eth0:0 10.5.5.2 netmask 255.255.255.0
$ sudo iptables -t nat -A POSTROUTING -o eth0 -d 10.5.5.0/24 -j MASQUERADE
$ sudo iptables -t nat -A PREROUTING -p tcp -m tcp --dport 80 -j DNAT --to-destination 10.5.5.1:80
# 关闭
$ sudo ifconfig eth0:0 down
$ sudo iptables -t nat -D POSTROUTING -o eth0 -d 10.5.5.0/24 -j MASQUERADE
$ sudo iptables -t nat -D PREROUTING -p tcp -m tcp --dport 80 -j DNAT --to-destination 10.5.5.1:80