#!/bin/bash

MAC=`ifconfig eth0|grep HWaddr|awk '{print $5}'`

for i in `echo $MAC|cut -d: -f3-|tr : ' '`; do
        [ -n "$IP" ] && IP=$IP.
        let c=0x$i
        IP=${IP}$c
done

GATEWAY=`echo $IP|cut -d. -f1-3`.1

ifconfig eth0 $IP netmask 255.255.255.0
route add default gw $GATEWAY