FORWARD默认是DROP的情况下，pptp服务器iptables 的配置

modprobe af_key

modprobe nf_conntrack_pptp nf_nat_pptp

echo 1 > /proc/sys/net/ipv4/ip_forward 

/sbin/iptables -t nat -A PREROUTING -p tcp --dport 1737 -j ACCEPT

/sbin/iptables -t nat -A PREROUTING -p 47 -j ACCEPT

iptables -A FORWARD -d 10.100.0.0/24 -j ACCEPT

iptables -A FORWARD -s 10.100.0.0/24 -j ACCEPT

iptables -A FORWARD -p tcp --syn -i ppp+ -j TCPMSS --set-mss 1356

#iptables -A FORWARD -p tcp --syn -s 10.100.0.0/24 -j TCPMSS --set-mss 1356

iptables -A FORWARD -p tcp --dport 1723 -j ACCEPT

iptables -A FORWARD -p 47 -j ACCEPT

/sbin/iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT

iptables -A INPUT -p tcp --dport 1723 -j ACCEPT

iptables -A INPUT -p 47 -j ACCEPT

iptables -t nat -A POSTROUTING -s 10.100.0.0/24 -o eth0 -j SNAT --to 192.168.0.2

iptables -t nat -A POSTROUTING -j SNAT --to-source 192.168.1.40