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Contoh kasus ipdhcp (dari isp):
Suatu perusahaan memiliki 10 client yang akan bisa akses keluar (internet) dan 1 server yang akan dijadikan sharing internet tapi tanpa proxy. Pada pembahasan kali ini saya akan mengulas tentang cara menyetting server sebagai gateway di linux (saya menggunakan distro RHEL 4 AS)
*pastikan linux sudah terinstall dengan benar (iptables sudah terinstall) acuan :
======# server #============================================
ip server(dhcp from isp) : 118.137.18.127 yang nantinya sebagai ip di eth0
netmask : langsung dapet dri isp juga(default)
ip server(static bo!!) : 192.168.0.1 (eth1) dan akan dijadikan gateway u/ client
netmask : 255.255.255.224
======# client #=============================================
pc client 1 - 10 menggunakan ip address : 192.168.0.2-192.168.0.11
gateway : 192.168.0.1
netmask : 255.255.255.224
Prakteknya :
A. Setting eth0
root@tbox# dhclient eth0
maka dengan sendirinya eth0 yg langsung terhubung dengan isp(dhcp) akan
mendapatkan ip yaitu 118.137.18.127 netmask 255.255.255.0
A.1. Setting ip_forwarding
root@tbox#joe /etc/sysctl.conf
>ubah net.ipv4.ip_forward = 0 menjadi net.ipv4.ip_forward = 1
atau kalau gak ada net.ipv4.ip_forward = 0 tambahin net.ipv4.ip_forward = 1
>simpen dengan menekan ctrl+kx
>kemudian restart networknya
root@tbox#/etc/init.d/network restart
Shutting down interface eth0 : [ OK ]
Shutting down loopback interface : [ OK ]
Disabling IPv4 packet forwarding : [ OK ]
Setting network parameters : [ OK ]
Bringing up loopback interface : [ OK ]
Bringing up interface eth0 : [ OK ]
root@tbox#ping 118.137.18.127
PING 118.137.18.127 (118.137.18.127): 56 data bytes
64 bytes from 118.137.18.127: icmp_seq=1 ttl=58 time=329.192 ms
64 bytes from 118.137.18.127: icmp_seq=2 ttl=58 time=320.970 ms
64 bytes from 118.137.18.127: icmp_seq=3 ttl=58 time=297.257 ms
atau (biar pasti coba lagi ping keluar)
root@tbox#ping plasa.com
PING plasa.com (202.134.0.12): 56 data bytes
64 bytes from 202.134.0.12: icmp_seq=0 ttl=246 time=12.779 ms
64 bytes from 202.134.0.12: icmp_seq=1 ttl=246 time=7.497 ms
64 bytes from 202.134.0.12: icmp_seq=2 ttl=246 time=12.228 ms
64 bytes from 202.134.0.12: icmp_seq=3 ttl=246 time=7.377 ms
64 bytes from 202.134.0.12: icmp_seq=4 ttl=246 time=7.391 ms selamat untuk langkah a kamu berhasil
B. Setting eth1
root@tbox#joe /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth1
BOOTPROTO=static
HWADDR=00:0C:29:BE:2F:27
ONBOOT=yes
IPADDR=192.168.0.1
BROADCAST=192.168.0.31
NETMASK=255.255.255.224
ONBOOT=yes
USERCTL=no lalu simpan dengan ctrl kx
>kemudian restart networknya lagi
root@tbox#/etc/init.d/network restart
Shutting down interface eth0: [ OK ]
Shutting down loopback interface: [ OK ]
Disabling IPv4 packet forwarding: [ OK ]
Setting network parameters: [ OK ]
Bringing up loopback interface: [ OK ]
Bringing up interface eth0: [ OK ]
Bringing up interface eth1: [ OK ]
>test ping lagi
root@tbox#ping 192.168.0.1
PING 192.168.0.1 (192.168.0.1): 56 data bytes
64 bytes from 192.168.0.1: icmp_seq=0 ttl=246 time=0.779 ms
64 bytes from 192.168.0.1: icmp_seq=1 ttl=246 time=0.497 ms
64 bytes from 192.168.0.1: icmp_seq=2 ttl=246 time=0.228 ms
64 bytes from 192.168.0.1: icmp_seq=3 ttl=246 time=0.377 ms
64 bytes from 192.168.0.1: icmp_seq=4 ttl=246 time=0.391 ms
okeh dah berhasil juga tuh...selamat yu guys..yukkk!!
root@tbox# /etc/init.d/named restart
Stopping named: [ OK ]
Starting named: [ OK ]
"Ketentuan CLIENT"
Tinggal Setting IP computer client dengan ketentuan di bawah ini :
IP : 192.168.0.2 - 192.168.0.30
GATEWAY : 192.168.0.1
NETMASK : 255.255.255.224
BROADCAST : 192.168.0.31
DNS : 192.168.0.1 misal :
Client01
===============================
IP : 192.168.0.2
GATEWAY : 192.168.0.1
NETMASK : 255.255.255.224
BROADCAST : 192.168.0.31
DNS : 192.168.0.1
Client02
===============================
IP : 192.168.0.3
GATEWAY : 192.168.0.1
NETMASK : 255.255.255.224
BROADCAST : 192.168.0.31
DNS : 192.168.0.1
dan seterusnya sesuai banyaknya client,yang berubah hanya IP untuk client windows maka setting IP di bagian Start Menu/Setting/Control Panel/Network setelah di setting ip client, maka coba ping ke 192.168.0.1 dari client, kalau berhasil berarti client dan gateway server-nya sudah tersambung. Setting gateway server supaya client bisa internat dengan menggunakan NAT
C. Matikan iptablesnya
root@tbox# /etc/init.d/iptables stop
Flushing all chains: [ OK ]
Removing user defined chains: [ OK ]
Resetting built-in chains to the default ACCEPT policy: [ OK ]
root@tbox#
D.Tambahkan iptables untuk Source NAt sesuai dengan ip di eth0
root@tbox# /sbin/iptables -t nat -A POSTROUTING -o eth0 -s 192.168.0.0/24 -j SNAT –to
source 118.137.18.127
root@tbox# /sbin/iptables-save > /etc/sysconfig/iptables
root@tbox# /etc/init.d/iptables restart
Flushing all current rules and user defined chains: [ OK ]
Clearing all current rules and user defined chains: [ OK ]
Applying iptables firewall rules: [ OK ]
root@tbox# iptables-save
Selesai sudah silahkan coba di client dengan browser ke sukaan kamu jika bisa internetan maka konfigurasi yang anda buat "berhasil"
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