Forward Proxy to another proxy
If you are in a corporate computer not directly connected to the internet, But connected to a outside network with a tunnel to the internet then you might need to double forward your traffic.
Case Study
Local Computer → Firewalled Connection → Github (access denied)
Local Computer → External Network (no direct internet) → NAT Server (not firewalled with internet access)
Description
The first connection is the default firewalled connection which is given in your corporate network. However, as you see basic connection to git servers like github over the https protocol is not allowed.
There is another network available an External Network with no direct internet access but instead uses a NAT server to connect to the internet. So how do we use the second connection to connect to the internet without Firewall restriction?
What we need
Our end result should be a direct connection from local computer to the NAT Server
Local Computer → Nat Server
Solution
First of all we need to install a squid forward proxy to proxy our traffic to the external network instead of the firewalled connection
Allow access to our computer or set of computer using this guide
Second since we have access to the NAT server from the external network do the same thing in there. Install a squid forward proxy and configure it
Our network should now look like
Local Computer → External Network (Squid1) → NAT Server (Squid2)
Now we can use unrestricted connection to the Internet from the External Network but not from the Local Computer
Lastly to finish our setup to the internet we have to add some tweaks to the squid1 configuration so it will forward all the traffic to squid2
# on squid1
vi /etc/squid/squid.conf# add the following statements
cache_peer NAT Server IP parent 3128 0 no-digestnever_direct allow all
Hook it up
Now test it on you local computer browser by setting proxy to Squid1:3128 port. And check your ip on ipinfo.com.
Chrome Proxy
Firefox Proxy Settings
If your ip is now NAT Server’s public IP then you should now have unrestricted access to the internet
