When your business hinges upon remote workers and remote offices, secure connections, and lots of data manipulation… how do you deal with some of your folks being extra remote? Granted the internet in 2020 is very different from the internet in say 2008 and the world has grown ever smaller as a result… but distance and all of the congested, intervening, network hops that come with it are still a reality. Particularly for remote workers living on other continents that have to interface regularly with systems in the United States as a part of their job.

The two big headaches for remote workers in other countries connecting to offices in the US are latency and bandwidth. In the past there were only and handful of solutions, most involving long-term contracts with a telcom and lengthy, complicated setups. I would argue that MPLS still falls squarely in this camp. SD-WAN has certainly improved on all of the above but it’s still enough of a headache that it typically involves contract terms and conversations with sales “engineers.”

I would like to propose something different using Azure.
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I have been taking a free networking class from Stanford University’s online “open source” education platform. I have really been enjoying the first unit of the course as it has started filling in some gaps in the foundation of my understanding regarding networking, the internet, and TCP/IP. I highly recommend this to anyone that has been in IT for a while but has never taken a more “academic” approach to their work. Okay, so that is my plug for free education. You can check out more here if interested: https://lagunita.stanford.edu/

OSI 7-Layer Model, TCP/IP 4-Layer Model
One of the gaps in my understanding of networking has to do with the OSI 7-layer networking model and the more simplified TCP/IP 4-Layer model (which was developed by DARPA? and predates the OSI Model). I didn’t even realize there was anything other than the 7-Layer model until taking this class and furthermore didn’t realize that while the OSI model gets talked about and referenced more frequently, academia (I think… and perhaps the industry) is shifting to using the simpler 4-layer model for discussion, understanding, and development regarding networking. Please don’t take any of this as gospel truth, this is just my understanding based on coursework and reading. I also find it much easier to think about and reference the 4-layer model. If you are curious how the two compare, this technet article is an interesting read, Technet: TCP/IP Protocol Architecture. Okay, so for this article, I will be sticking with what I am most comfortable with at this point and will be talking about and referencing the 4-layer TCP/IP model and discussing how VPN works. (more…)

In a previous post I dealt with setting up an OpenVPN Community Edition server which is the free version of OpenVPN. I had initially hoped to use Authy for two-factor authentication in addition to LDAP but later found out that wasn’t going to work. So now I am looking at using DUO for two-factor authentication and OpenVPN Access Server.

Access Server is the “paid” version of OpenVPN and is significantly easier to install and configure vs. the open-source community edition. The two different products fulfill the same function and rely on the same technology to do so, but the underlying structure of Access Server is significantly different from the community edition.

Just to be clear, if you don’t need two-factor authentication, and don’t mind applying a bit of digital elbow grease, I highly recommend going with the community edition of OpenVPN as it is extremely scalable with no licensing fees. That being said, Access Server is decently economical, especially compared to putting in a hardware device like a Fortigate or Cyberroam UTM box.

This guide assumes you have an Ubuntu 13 box to work with, have full root access, know your way around the linux command-line, and have a basic understanding of networking concepts including VPN.

Let’s dive in!

Before you go any further, if you plan on using LDAP/Microsoft Active Directory, you need to make sure all of the proper ports are open between your Active Directory Domain Controller and your OpenVPN server. You can see which ports are needed for AD traffic here: What ports on the firewall should be open between Domain Controllers and Member Servers?

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