DNS and Virtual Hosting: A Personal Journey

by Joche Ojeda | Mar 11, 2025 | network

DNS and Virtual Hosting: A Personal Journey

In this article, I’m going to talk about a topic I’ve been working on lately because I’m creating a course on how to host ASP.NET Core applications on Linux. This is a trick that I learned a really long time ago.

I was talking with one of my students, Lance, who asked me when I learned all this hosting and server stuff. It’s actually a nice story.

My Early Server Adventures

When I was around 16 years old, I got a book on networking and figured out how to find free public IPs on my Internet provider’s network. A few years later, when I was 19, I got a book on Windows 2000 Server and managed to get a copy of that Windows version.

I had a great combination of resources:

Public IPs that I was “borrowing” from my Internet provider
A copy of Windows Server
An extra machine (at that time, we only had one computer at home, unlike now where I have about 5 computers)

I formatted the extra computer using Windows Server 2000 and set up DNS using a program called Simple DNS. I also set up the IIS web server. Finally, for the first time in my life, I could host a domain from a computer at home.

In El Salvador, .sv domains were free at that time—you just needed to fill out a form and you could get them for free for many years. Now they’re quite expensive, around $50, compared to normal domains.

The Magic of Virtual Hosting

What I learned was that you can host multiple websites or web applications sharing the same IP without having to change ports by using a hostname or domain name instead.

Here’s how DNS works: When you have an internet connection, it has several parts—the IP address, the public mask, the gateway, and the DNS servers. The DNS servers essentially house a simple file where they have translations: this domain (like HotCoder.com) translates to this IP address. They make IP addresses human-readable.

Once requests go to the server side, the server checks which domain name is being requested and then picks from all the websites being hosted on that server and responds accordingly.

Creating DNS records was tricky the first time. I spent a lot of time reading about it. The internet wasn’t like it is now—we didn’t have AI to help us. I had to figure it out with books, and growing up in El Salvador, we didn’t always have the newest or most accurate books available.

The Hosts File: A Local DNS

In the most basic setup, you need a record which says “this domain goes to this IP,” and then maybe a CNAME record that does something similar. That’s what DNS servers do—they maintain these translation tables.

Each computer also has its own translation table, which is a text file. In Windows, it’s called the “hosts” file. If you’ve used computers for development, you probably know that there’s an IP address reserved for localhost: 127.0.0.1. When you type “localhost” in the browser, it translates to that IP address.

This translation doesn’t require an external network request. Instead, your computer checks the hosts file, where you can set up the same domain-to-IP translations locally. This is how you can test domains without actually buying them. You can say “google.com will be forwarded to this IP address” which can be on your own computer.

A Real-World Application

I used this principle just this morning. I have an old MSI computer from 2018—still a solid machine with an i7 processor and 64GB of RAM. I reformatted it last week and set up the Hyper-V server. Inside Hyper-V, I set up an Ubuntu machine to emulate hosting, and installed a virtual hosting manager called Webmin.

I know I could do everything via command line, but why write a lot of text when you can use a user interface?

Recently, we’ve been having problems with our servers. My business partner Javier (who’s like a brother to me) mentioned that we have many test servers without clear documentation of what’s inside each one. We decided to format some of them to make them clean test servers again.

One of our servers that was failing happens to host my blog—the very one you’re reading right now! Yesterday, Javier messaged me early in the morning (7 AM for me in Europe, around 9 PM for him in America) to tell me my blog was down. There seemed to be a problem with the server that I couldn’t immediately identify.

We decided to move to a bigger server. I created a backup of the virtual server (something I’ll discuss in a different post) and moved it to the Hyper-V virtual machine on my MSI computer. I didn’t want to redirect my real IP address and DNS servers to my home computer—that would be messy and prevent access to my blog temporarily.

Instead, I modified the hosts file on my computer to point to the private internal IP of that virtual server. This allowed me to test everything locally before making any public DNS changes.

Understanding DNS: A Practical Example

Let me explain how DNS actually works with a simple example using the domain jocheojeda.com and an IP address of 203.0.113.42.

How DNS Resolution Works with ISP DNS Servers

When you type jocheojeda.com in your browser, here’s what happens:

Your browser asks your operating system to resolve jocheojeda.com
Your OS checks its local DNS cache, doesn’t find it, and then asks your ISP’s DNS server
If the ISP’s DNS server doesn’t know, it asks the root DNS servers, which direct it to the appropriate Top-Level Domain (TLD) servers for .com
The TLD servers direct the ISP DNS to the authoritative DNS servers for jocheojeda.com
The authoritative DNS server responds with the A record: jocheojeda.com -> 203.0.113.42
Your ISP DNS server caches this information and passes it back to your computer
Your browser can now connect directly to the web server at 203.0.113.42

DNS Records Explained

A Record (Address Record)

An A record maps a domain name directly to an IPv4 address:

jocheojeda.com.    IN    A    203.0.113.42

This tells DNS servers that when someone asks for jocheojeda.com, they should be directed to the server at 203.0.113.42.

CNAME Record (Canonical Name)

A CNAME record maps one domain name to another domain name:

www.jocheojeda.com.    IN    CNAME    jocheojeda.com.
blog.jocheojeda.com.   IN    CNAME    jocheojeda.com.

This means that www.jocheojeda.com and blog.jocheojeda.com are aliases for jocheojeda.com. When someone visits either of these subdomains, DNS will first resolve them to jocheojeda.com, and then resolve that to 203.0.113.42.

Using the Windows Hosts File

Now, let’s see what happens when you use the hosts file instead:

When using the hosts file:

Your browser asks your operating system to resolve jocheojeda.com
Your OS checks the hosts file first, before any external DNS servers
It finds an entry: 192.168.1.10 jocheojeda.com
The OS immediately returns the IP 192.168.1.10 to your browser
Your browser connects to 192.168.1.10 instead of the actual public IP
The external DNS servers are never consulted

The Windows hosts file is located at C:\Windows\System32\drivers\etc\hosts. A typical entry might look like:

# For local development
192.168.1.10    jocheojeda.com
192.168.1.10    www.jocheojeda.com
192.168.1.10    api.jocheojeda.com

This is incredibly useful for:

Testing websites locally before going live
Testing different server configurations without changing public DNS
Redirecting domains during development or troubleshooting
Blocking certain websites by pointing them to 127.0.0.1

Why This Matters for Development

By modifying your hosts file, you can work on multiple websites locally, all running on the same machine but accessible via different domain names. This perfectly mimics how virtual hosting works on real servers, but without needing to change any public DNS records.

This technique saved me when my blog server was failing. I could test everything locally using my actual domain name in the browser, making sure everything was working correctly before changing any public DNS settings.

Conclusion

Understanding DNS and how to manipulate it locally via the hosts file is a powerful skill for any developer or system administrator. It allows you to test complex multi-domain setups without affecting your live environment, and can be a lifesaver when troubleshooting server issues.

In future posts, I’ll dive deeper into server virtualization and how to efficiently manage multiple web applications on a single server.

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Windows Server Setup Guide with PowerShell

by Joche Ojeda | Mar 2, 2025 | PowerShell, WebServers, Windows Os

In one of our meetings with Javier, we were discussing how many servers we have in the office. In the end, it turned out that we have a lot of servers, both Windows and Linux. So we decided to take a look and see what is running on each of the servers. A lot of those servers are actually test servers used to test deployments or to show something to a customer. A few of them were just full of examples or basically nothing, so I decided to format them and rebuild the installation.

I decided to start with the Windows server, so this post is going to be about the tools that I use to set up the Windows 2016 server.

There were a few tasks that I needed to accomplish that I usually do using the UI, and most of them are a pain in the ****. There is no other way to describe it, so I decided to create scripts instead so I can replicate it easily between servers.

Disable Internet Explorer Enhanced Security

The first task that I do when I set up a Windows Server is to disable Internet Explorer Enhanced Security. If you have used that type of security before, basically it means that you need to allow or whitelist every URL in the page that you’re browsing and the related pages in the page that you’re browsing. So it’s like 100 clicks per page. To remove the enhanced security, you need to go to the Windows features and turn it off there and then restart. So I created a script that does that for me. In one click, I can just disable the security so I can use Internet Explorer to actually download something newer like Microsoft Edge.

Disable internet explorer Enhanced Security

Set Up Web Server Role

The next step after disabling the enhanced security is to set up the Web Server role in Windows Server. This doesn’t come out of the box; you have to actually add the role to the server. For that, I will use another script, and the script will also install Web Deploy, which is the functionality that allows you to do remote deploying into an IIS server.

Setup Web Server Role

Fix Web Deploy Permissions (Optional)

Now here is an extra step. This step is optional. For some reason, in some of the servers, even though you have a clean installation, there will be a problem setting up the Web Deploy functionality. It’s a permission problem basically. So there is a script to fix that. You have to run the first script that installs the Web Server and the remote Web Deploy functionality. This is optional; you should use it only in case your Web Deploy doesn’t work.

Fix web deploy permissions

Set Up SQL Server Express

The next step for setting up the server is to set up SQL Server Express, and I have a script for that. I will paste it here, but for some reason, the script always fails in the way that you download and try to deploy it on the server. What happens is that the process always gets busy and the files get locked. So I will have to come back to that one later, but I will post the script here just to remember it.

SqlServer Express install

Enable Remote SQL Server Access (Optional)

OK, the next script is also optional. In our test servers, we usually allow remote access to the SQL Server database because we need to either restore a backup or create a database. For this, we need to do two things: open the firewall port for the database and also enable TCP connection from the outside. So here is a script for that too.

Enable Remote SQL Server Access

So that will be it for this post. Let me know which script you would like to have to automate your server setup.