route del default gw 192.168.4.1 //删除原有的网断
route add default gw 58.155.94.252
iptables -t nat -L -n
echo "1" > /proc/sys/net/ipv4/ip_forward
modprobe ip_tables
modprobe ip_nat_ftp
iptables -F INPUT
iptables -F FORWARD
iptables -F POSTROUTING -t nat
iptables -t nat -A POSTROUTING -s 192.168.3.0/24 -o eth1 -j SNAT --to 58.155.94.252 //实现由58.155.94.252（外网）到192.168.3.0/24这个网断的转发
service iptables save
service iptables start