The Domain Name System (DNS) is one of the fundamental components of the Internet, since it has the task of converting human-readable domain names into IP addresses that computer systems can interpret.
But just how important is this exactly? To get an idea, Vercara’s UltraDNS platform processed 41.97 trillion DNS queries in 2023 alone, averaging 115 billion queries per day.
While the DNS system generally resolves domain names into public Internet IP addresses, sometimes we come across records that point to local IPs, also known as internal or private IPs. The practice of DNS pointing to local IPs can be quite useful in certain scenarios, such as development environments, managing internal networks, or simply running tests.
In this article, we’ll walk you through everything you need to know about DNS pointing to local IPs, including its uses, benefits, risks, limitations, and more.
Table of Contents
An Introduction to DNS and IPs
The DNS system works like a kind of phonebook for the Internet. Every website on the Internet has an IP address, which is essentially a string of numbers that computers use to communicate with each other. For a computer, this is no problem, but for a person, remembering so many numbers can quickly become overwhelming.
The solution, of course, is DNS, which converts easy-to-remember domain names, like example.com, into an IP address that a system can understand. Amazon AWS states that the DNS controls “which server an end user will reach when they type a domain name into their web browser.“
Most of the DNS system’s activity involves public IP addresses that are accessible over the Internet. But there are also private or local IPs, as we mentioned earlier, and these are typically used by internal networks in companies, schools, homes, and so on.
Local IPs, such as 192.168.x.x or 10.x.x.x, are not accessible from outside the local network, and they are essential for internal communication between devices within the same network.
When we perform DNS pointing to local IPs, we are essentially mapping a domain name to a local IP. This can be very useful in certain cases, for example, if we work in web development, it’s great for testing applications or websites in a controlled environment before deploying them into production.
In essence, using DNS pointing to local IPs is a way to take advantage of the conveniences of DNS while keeping traffic within our internal network.
How DNS Works with Local IPs
Normally, when you type a domain name into your browser, your computer queries a DNS server to get the domain’s public IP address, allowing you to access the website in question. This process lets us connect to websites and services all around the world through the Internet.
By default, it’s assumed that the IP address of a domain is accessible over the Internet, which makes perfect sense when we’re talking about public websites. But what happens in the case of a DNS pointing to local IPs?
When a DNS record points to a local IP, the process is similar, but the destination is different. Instead of resolving to an Internet-based IP, it resolves to an internal network, like a web server running on your own device or a development server in your office.
The DNS system does not distinguish whether the IP address requested is public or private; it simply returns the value assigned in the record. Thanks to this, it’s possible to configure DNS pointing to local IPs and link a domain or subdomain to resources within a local network.
For example, if you have a file server at the internal address 192.168.1.40, instead of remembering that number, you could set up a name like files.local to access it, provided that the necessary record exists, of course.
While this flexibility is useful, it also means administrators must be aware of potential vulnerabilities, such as CVEs affecting DNS Servers, which can have a direct impact on both public and private DNS setups.
Methods to Point DNS to Local IPs
There are several ways to set up DNS pointing to local IPs, depending on your needs and technical setup.
The simplest method is to use a text editor to modify your system’s hosts file. Every operating system has one, and by adding a line for a specific domain, you can point it to any IP address you want, completely bypassing public DNS results. For example, adding 192.168.1.10 test.local would point that domain name to that IP, and for your computer, that domain would resolve internally.
When dealing with larger networks, the approach changes somewhat, and in that case, it’s better to have a local DNS system. Tools like BIND or dnsmasq can be used to create these custom entries within a private DNS network. With this method, you only need to configure the rule once, and every device on the network will follow it. Just remember to avoid issues like SPF misconfigurations and MX misconfigurations, both of which could disrupt email delivery.
Another option for achieving DNS pointing to local IPs is setting up a DNS override on your router. Many modern routers allow you to define custom DNS entries, making it possible to direct traffic for certain domains into your private network.
Benefits of DNS Pointing to Local IPs
DNS pointing to local IPs offers several practical benefits.
- Web Development: When it comes to web development, instead of publishing a work-in-progress version of a site online, you can configure it within your local network and point a domain like mysite.local to an internal IP. This makes it possible to test in a realistic environment without exposing unfinished work to the Internet.
- Businesses and Organizations: Different types of companies can also benefit from this practice, particularly when it comes to internal services. For example, a company might host an intranet, a file server, or even configure access to a printer, all within its local network and using internal domain mappings. Domains make these setups friendlier and easier to remember, but keep in mind being careful with your DNS records to prevent abuse from phishing subdomains.
- Security: There is also a security advantage in DNS pointing to local IPs. By keeping certain resources accessible only from within a local network, organizations reduce their exposure to the outside world, lowering the risk of unwanted access. In addition, since the traffic stays inside the local network, it will usually be faster than going through a public one.
Risks of DNS pointing to local IPs
While using DNS pointing to local IPs can bring us several benefits, it’s also true that it comes with certain risks we should not ignore.
- Misconfiguration: One of the main issues is falling into a DNS misconfiguration. For example, if a domain needs to resolve publicly but is accidentally pointed to a local IP, that domain will no longer be visible on the Internet, affecting any service that depends on it.
- Security: There is always the security factor to consider, particularly when it comes to security misconfigurations. By mistake, resources that should remain private might be exposed. This could give unauthorized parties access to sensitive information or details about our infrastructure, making it easier for them to spot vulnerabilities.
- Management: Another potential risk arises when managing multiple records across multiple devices, which can lead to inconsistencies. This is especially likely in larger environments where internal DNS rules are not centralized.
If we are going to use DNS pointing to local IPs, it’s important to plan it carefully and document every step taken. That way, if problems occur, it’s easier to trace what went wrong.
Bottom Line
DNS pointing to local IPs is a simple but powerful practice that can make day-to-day operations smoother, whether for web developers, businesses, or even home networks. By using it, we can test projects in safe environments, simplify access to internal services, and reduce exposure to the Internet when security is a concern.
At the same time, it highlights the versatility of the DNS system, which adapts not only to global Internet needs but also to private networks. Understanding how and when to apply this technique can save time, improve efficiency, and strengthen local infrastructure.