IP설정 문제(초보입니다)

아래와 같이 하고나서 ifconfig 하면 저 IP들이 나오는데
재부팅하고 나면 저 IP가 안나오고 초기에 나오던 IP만 나옵니다
그리고 저 설정시
/bin/sh <---입력해서 나머지들 입력을해주는건지
완전 초보이니 자세히 설명해주신분 계신가요
꼭 부탁드립니다



#!/bin/sh

# ETH0 Router <=> Server Lan Card Routing
/sbin/ip addr add 121.xxx.xx.x/27    brd 121. xxx.xx.xx   dev eth0 scope link
/sbin/ip link set eth0 up

# ETH1 Public IP Setting
/sbin/ip addr add 121.xxx.xx.x/24      brd 121.xxx.xx.xxx      dev eth1 scope global
/sbin/ip addr add 121.xxx.xx.x/24      brd 121.xxx.xx.xxx      dev eth1 scope global
/sbin/ip link set eth1 up

# ETH1 Private IP Setting
/sbin/ifconfig eth1:0 10.xx.x.x netmask 255.255.255.0
/sbin/ifconfig eth1:1 10.xx.x.x netmask 255.255.255.0
/sbin/ifconfig eth1:2 10.xx.x.x netmask 255.255.255.0
/sbin/ifconfig eth1:3 10.xx.x.x netmask 255.255.255.0
/sbin/ifconfig eth1:4 100.xx.x.x netmask 255.255.255.0

# Default Gateway Setting
/sbin/route add -net default gw  121.xx.x.x

# ETH1 Private NAT
/sbin/iptables -t nat -A POSTROUTING -s 10.xx.x.x/24 -d 0/0 -j MASQUERADE
/sbin/iptables -t nat -A POSTROUTING -s 10.xx.x.x/24 -d 0/0 -j MASQUERADE
/sbin/iptables -t nat -A POSTROUTING -s 10.xx.x.x/24 -d 0/0 -j MASQUERADE
/sbin/iptables -t nat -A POSTROUTING -s 10.xx.x.x/24 -d 0/0 -j MASQUERADE
/sbin/iptables -t nat -A POSTROUTING -s 100.xx.x.x/24 -d 0/0 -j MASQUERADE

/usr/local/hsdhcp/bin/hskern -p 121.10.xx.x.x
/usr/local/hsdhcp/bin/hskern -s 10.xx..x.x  10.xx.x.x 10.xx.x.x 100.xxx.xxx.x