此处使用Centos7

systemctl disable firewalld; #禁用系统自带防火墙
systemctl stop firewalld; #停止

安装iptables

yum install -y iptables-services iptables-devel.x86_64 iptables.x86_64
systemctl enable iptables; 
systemctl start iptables;

启用转发流量

sed -i 's/net.ipv4.ip_forward = 0/net.ipv4.ip_forward = 1/g' /etc/sysctl.conf sysctl -p

清楚iptables表

iptables -F iptables -t nat -F service iptables save

添加tcp或者udp规则

iptables -t nat -A PREROUTING -p tcp --dport [源端口号] -j DNAT --to-destination [目标IP:目标端口号] 
iptables -t nat -A POSTROUTING -p tcp -d [目标IP] --dport [目标端口号] -j SNAT --to-source [中转服务器IP] 

iptables -t nat -A PREROUTING -p udp --dport [源端口号] -j DNAT --to-destination [目标IP:目标端口号] 
iptables -t nat -A POSTROUTING -p udp -d [目标IP] --dport [目标端口号] -j SNAT --to-source [中转服务器IP]