Squid Proxy Server Configuration

Sure Squid Server is a popular open source Proxy and Web Cache Server. It has a variety of uses, from speeding up a Web Server by caching repeated requests, to caching Web, name server query , and other network lookups for a group of people sharing network resources. It is primarily designed to run on Linux / Unix-like systems. Squid is a high-performance proxy caching server for Web clients, supporting FTP, gopher, and HTTP data objects. Unlike traditional caching software, Squid handles all requests in a single, non-blocking, I/O-driven process. Squid keeps meta data and especially hot objects cached in RAM, caches DNS lookups, supports non-blocking DNS lookups, and implements negative caching of failed requests. 

Install Squid on CentOS / REDHAT

 # yum install squid

Squid Configuration

Squid configuration file located at /etc/squid/squid.conf. Open file using a text editor:

# vi /etc/squid/squid.conf

At least you need to define ACL (access control list) to work with squid. The defaults port is TCP 3128. Following example ACL allowing access from your local networks 192.168.1.0/24 and 192.168.2.0/24. Make sure you adapt to list your internal IP networks from where browsing should be allowed:

acl our_networks src 192.168.1.0/24 192.168.2.0/24

http_access allow our_networks

Save and close the file. Start squid proxy server:

# chkconfig squid on

# /etc/init.d/squid start

Output:

init_cache_dir /var/spool/squid... Starting squid: . [ OK ]

Verify port 3128 is open:

# netstat -tulpn | grep 3128

Output:

tcp 0 0 0.0.0.0:3128 0.0.0.0:* LISTEN 20653/(squid)

Open TCP port 3128

Finally make sure iptables is allowing to access squid proxy server. Just open /etc/sysconfig/iptables file:

# vi /etc/sysconfig/iptables

Append configuration:

-A RH-Firewall-1-INPUT -m state --state NEW,ESTABLISHED,RELATED -m tcp -p tcp --dport 3128 -j ACCEPT

Restart iptables based firewall:

# /etc/init.d/iptables restart

Output:

Flushing firewall rules: [ OK ]

Setting chains to policy ACCEPT: filter [ OK ]

Unloading iptables modules: [ OK ]

Applying iptables firewall rules: [ OK ]

Loading additional iptables modules: ip_conntrack_netbios_n [ OK ]