How do I connect to a VPN going through a proxy?
I am currently at a client and they are using a Proxy to connect the users to the internet. I want to VPN back into my company to retrieve some files.
I tried applications like Proxifier, but for some odd reason when I try and configure the Proxy server on it, it always fails to connect to it, but using the proxy directly through Firefox and IE works…
So, how can I do this, or is it not possible?
Best Answer
I found myself in a very similar situation more than once. If you follow IANA port assignment rules, it is as slhck says: you cannot do it without asking the administrator to allow an outgoing connection to your VPN (e.g. port 1194 UDP is the default for OpenVPN).
However, I managed to solve that problem by breaking the rules and assigning TCP port number 443 (HTTPS) to my VPN server. This worked for me because the network that I connected from did not actually proxy TCP port 443: they simply forwarded TCP:443 packets transparently -- probably to avoid the hassle of configuring an HTTPS proxy. This post here discusses HTTPS proxies, which might prevent this solution from working.
Recently I also learned that OpenVPN supports proxies, as shown in this OpenVPN howto page. I haven't tested that, but it might work.
It all depends on how strict is network security at the place you are... In the end it might just be easier (and more ethical) to just ask your client's IT folks to help you.
Please notice that using TCP for a VPN is not advised, as it introduces an extra layer of TCP overhead, as discussed in this post.