换IP的几种方法：

1、没有配内网IP的话

sed -i s#ONBOOT=no#ONBOOT=yes#g /etc/sysconfig/network-scripts/ifcfg-eth1

cat  >>/etc/sysconfig/network-scripts/ifcfg-eth1<<EOF

IPADDR=192.168.20.157

NETMASK=255.255.255.0

EOF

2、如果配了，可以

A直接修改,省略

B利用sed替换，省略

C用脚本来替换 

#!/bin/bash

#qq:11111110

#version 1.0

#this script for change eth

echo "press input eth0 or eth1"

read A

eth=$A

IFCFG=/etc/sysconfig/network-scripts/ifcfg-${eth}

ADDR=`ifconfig ${eth} |sed -ne 's/^.* inet addr:\([^ ]*\).*$/\1/gp'`

MASK=`ifconfig ${eth} |sed -ne 's/^.* Mask:\([^ ]*\).*$/\1/gp'`

echo "你要替换的地址是${eth} ${ADDR} ${MASK}"

echo "you want change :"

read  a b

echo "替换IP后的地址为${eth} $a $b" 

echo "ok?no?"

read c

if [ "$c" == "ok"  ]

    then

                cp ${IFCFG} ${IFCFG}.bak

                sed -i "s/$ADDR/$a/g" $IFCFG

                sed -i "s/$MASK/$b/g" $IFCFG

echo "now: $eth $a $b "         

fi