动态跟踪我爸 PPPoE 上网的 IP 并重定向到固定地址的脚本（bchyi.sh）

这样就不用每次都登录到 server 上 ifconfig 去查看了^_^

#! /bin/bash
# get device name on platinum server
DEVICE=`ifconfig|awk '/ppp[1-9]/{print $1}'`
if [ "$DEVICE" != "" ]
then
        # get the device named pppxx's IP
        NEW_IP=`ifconfig $DEVICE|awk -F"[ :]" '/inet/{print $16}'`
        # get the OLD IP if I found
        OLD_IP=`iptables-save -t nat|awk '/5.5.5.5/{print $NF}'`
        if [ "$OLD_IP" != "$NEW_IP" ]
        then
                if [ "$OLD_IP" != "" ]
                then
                        # delete the OLD rule about the OLD IP
                        iptables -t nat -D PREROUTING -d 5.5.5.5 -j DNAT --to $OLD_IP
                fi
                # insert the NEW rule use NEW IP
                iptables -t nat -I PREROUTING -d 5.5.5.5 -j DNAT --to $NEW_IP
        fi
fi