Cannot ping google.com from Ubuntu terminal behind a proxy server
I am connected to the internet through a proxy server. I am using an Ubuntu installation and have made the appropriate network setting changes including in the files /etc/bash.bashrc and /etc/apt/apt.conf files. After these proxy changes that I have made, I am able to download from Ubuntu repositories on the internet.
The problem that I want to understand and solve is this : From the terminal, I am able to ping addresses that I am connected to on my intranet. However, I am not able to ping addresses on the internet! Why might this be? A technical explanation would be really appreciated. And how can I get around this and use commands like wget, ping etc (neither of which work right now) like on any other direct internet connection?
Note : I have tried export http_proxy variable with the appropriate username and password for my proxy server as shown here but ping still does not work.
Answer
The usual reason for a proxy server is to isolate internal machines, and force them out through a central point in order to manage bandwidth, content and/or security concerns. Organizations who employ this mechanism will often disable routes from internal machines directly outside.
In this configuration, you are not truly connected to the internet, just the intranet which includes a server that proxies data from the internet to the intranet.
wget can work, if you set up the http_proxy environment variable, and perhaps add the --proxy-user and --proxy-password parameters. It is, in fact, a royal PITA.
ping will not work, if your network admin has disabled direct access to the larger network. To get ping working, you'll have to petition to have an exception for your workstation/server to be granted a direct route to the internet.
A technical explanation would be really appreciated.
Your network admin has disabled direct access to the internet, probably by dropping packets that are headed outside the intranet.