squid – your transparent proxy friend

Still my favourite light and fast web proxy is Squid. Its very easy to setup and get running on almost all flavours of linux. You can find it here http://www.squid-cache.org/ but will probably find it in your local package manager…

This is for more my own reference… as i don’t think too many people have the need for a transparent proxy. You only need one NIC configured on your VM / machine as its most probably on the same subnet as your dsl etc…

1. Setup squid working as a proxy first!

Set the default gateway on the NIC to your router. I also added a default route 0.0.0.0 sub 0.0.0.0 to the router also just in case the default route didn’t work. But seemed to!

Setup DNS! remember you should be able to resolve a name to an IP without issues (can cause most of the problems) Point your default DNS to your router (most have built in DNS forwarders), else you can just use your ISP’s DNS’s

2. Change the squid.config to have the necessary changes to act as a transparent proxy;

nano /etc/squid/squid.conf

http_port 3128 transparent

3. Put this into the startup script; (usually in rc.d under etc) rc.local

iptables -t nat -A PREROUTING -i eth0 -p tcp –dport 80 -j REDIRECT –to-port 3128

This redirects standard tcp requests to 3128 (squid’s port)… transparent to user

4. Ensure that IP forwarding is ENABLED;

change ip_forward from 0 to 1 (usually a txt file somewhere with 0 in it), do a search and you will find it… most probably in the ipv4 directory. This way all 443 (https and other apps) can forward to the web without issue…

echo 1 > /proc/sys/net/ipv4/ip_forward

Should be it…. else good luck!

Update: I have done an updated post about configuring open solaris as a transparent proxy here : http://sigtar.com/2009/04/22/opensolaris-configuring-squid-as-transparent-proxy/

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