Configure iptables proxy for Internet access in Linux

In linux, iptables proxy is used for Internet access. 1. Gateway/proxy server (proxyserver) iptables: the firewall software iptables in linux has two features: 1, firwall2, nat address translation rpm-qa | grepiptablesiptables-1.2.11-3.1.RHEL4serviceiptalbesstar in linux IptablesProxy surfing
1. Gateway/proxy server)
Iptables: firewall software in linux
Iptables has two functions: 1. firwall
2. nat address translation
Rpm-qa | grep iptables
Iptables-1.2.11-3.1.RHEL4
Service iptalbes start
Iptables has two tables: 1. when you use the filter table, it is regarded as a firewall.
2. when you use a nat table, it considers you as a proxy for Internet access.
Iptables-t nat-L
Below the nat table is the Chain)
1. PREROUTING
2. POSTROUTING
3. OUTPUT
Iptables-t nat-A (add) POSTROUTING (add a postrouting chain)-s202.106.20.0/24 (which network segment is active/which computers are going online)-j (perform an action) MASQUERADE (IP address disguise)
Target
Prot
Source
Destination
Echo "1">/proc/sys/net/ipv4/ip_forward
To enable the proxy to access the internet permanently, we need to write a script (executable file) in linux)
All scripts are stored in cd/bin.
Cd/bin
Touch daili
Chmod a + x daili
Vi daili
#! /Bin/bash
Adsl-stop
Adsl-start
Route add default ppp0
Iptables-t nat-F
Iptables-t filter-F
Echo "1">/proc/sys/net/ipv4/ip_forward
Iptables-t nat-a postrouting-s 202.106.20.0/24-j MASQUERADE
Iptables-t nat-a postrouting-s 192.168.0.0/24-j MASQUERADE
If you want to automatically drive the following machine to access the Internet at every boot, execute the following command:
Vi/etc/rc. local
Write/bin/daili to rc. local.
(Note: The Gateway of the nat client points to the ip address of the computer used as a proxy to access the Internet)
Squid proxy (cache proxy)
Port: tcp 3128
Rpm-qa | grep squid
Squid-2.5.STABLE6-3
Vi/etc/squid. conf
Http_port 3128
Cache_mem 8 MB
Cache_dir ufs/var/spool/squid 100 16 256
(100 is the amount of 256 MB that can be stored in this directory. this can be changed. it will create 16 sub-directories in this directory to store webpages, and sub-directories will be created under 16 sub-directories)
Acl LAN1 src 202.106.20.0/24
Acl LAN2 src 192.168.0.0/24
Http_access allow localhost LAN1 LAN2
Http_access deny
Squid-z
Service squid start
(Note: the squid client needs to set the ip address of the proxy server under the LAN connection settings in Internet options in IE browser and the squid port 3128)