Access Machines by DNS Name with DD-WRT - A How-To Guide

Utilizing DNS Names with DD-WRT Routers

Having previously demonstrated the process of configuring static IPs within your network, we will now explore the benefits of employing DNS for enhanced convenience and streamlined management.

This guide details the steps required to access your devices using descriptive DNS names when operating a router with DD-WRT firmware.

The Advantages of DNS Names

Instead of remembering numerical IP addresses, DNS names offer a more user-friendly method for identifying and connecting to devices on your network.

This approach simplifies network administration and improves overall usability.

Accessing Machines via DNS

DD-WRT allows you to assign custom DNS names to devices connected to your router.

This functionality enables access to your machines simply by typing the assigned name into a web browser or other network application.

The process involves configuring the DD-WRT interface to resolve these names to the corresponding IP addresses.

Image by Henk L

By leveraging DNS, you can create a more intuitive and manageable network environment.

The Advantage of DNS over Static IPs

In our previous guide on configuring static DHCP on your DD-WRT router, we detailed the process of assigning consistent IP addresses to devices on your network. Knowing a device’s IP allows direct access, but relying on IP addresses can be cumbersome.

Using names is far more intuitive than remembering numerical IP addresses. However, the benefits of static IPs are decreasing with the increasing prevalence of UPnP.

Challenges with Static IP Reservations

Furthermore, setting up static reservations requires identifying MAC addresses and other technical details, which can be inconvenient for many users.

What if a more streamlined solution existed, eliminating the need to memorize IPs altogether?

Introducing DNS for Simplified Network Access

This is where the Domain Name System (DNS) provides a superior alternative.

DNS allows you to assign memorable names to your devices, simplifying network access and management. It effectively translates human-readable names into the IP addresses that computers use.

Why DNS is a Better Solution

• Ease of Use: Access devices by name instead of IP address.
• Dynamic Environments: Works seamlessly even if IP addresses change.
• Reduced Complexity: Eliminates the need for manual IP tracking.

By leveraging DNS, you can create a more user-friendly and efficient network experience, moving beyond the limitations of static IP configurations.

Understanding Hostname Resolution Issues

You can successfully connect to devices on your network using their IP addresses, such as with the ping command. However, attempts to connect using hostnames – like "mydesktop" or "mylaptop" – are often unreliable.

The Role of DNS

This inconsistency typically stems from problems with Domain Name System (DNS) resolution. DNS translates human-readable hostnames into the numerical IP addresses computers use to communicate.

How Hostname Resolution Works

When you type a hostname, your computer queries a DNS server to find the corresponding IP address. If the DNS server can't find a record for that hostname, the connection will fail.

Common Causes of Failure

Several factors can contribute to DNS resolution failures. These include incorrect DNS server settings, issues with the local hosts file, or problems with the network's DNS infrastructure.

Troubleshooting Steps

Here are some steps you can take to diagnose and resolve the issue:

• Verify DNS Server Settings: Ensure your network adapter is configured to use valid and functioning DNS servers.
• Check the Hosts File: The hosts file on your computer can override DNS settings. Confirm that the hostname isn't incorrectly mapped in this file.
• Flush DNS Cache: Clearing your computer's DNS cache can resolve issues caused by outdated or corrupted DNS records.
• Restart Network Services: Restarting network services on your computer can sometimes resolve temporary DNS-related problems.

Local Network Considerations

On a local network, hostname resolution often relies on a local DNS server or the NetBIOS name resolution protocol. Problems with these local services can also cause intermittent hostname resolution failures.

Further Investigation

If the problem persists, further investigation may be needed to identify issues with your network's DNS configuration or the devices themselves. Consider consulting your network administrator for assistance.

Understanding DNS Resolution Issues

Many devices encounter difficulties translating hostnames into IP addresses due to a missing, yet crucial, configuration element: the DNS suffix.

When a computer attempts to resolve a hostname to its corresponding IP address, it utilizes several methods, one of which involves querying a Domain Naming System (DNS) server.

The Role of Fully Qualified Domain Names (FQDNs)

To successfully query a DNS server, the client must formulate its request as a Fully Qualified Domain Name (FQDN).

An FQDN is constructed from the hostname – for example, "mydesktop" – combined with the DNS zone to which it belongs, such as "geek.lan".

Therefore, in a network utilizing "geek.lan" as its DNS zone, the FQDNs for hosts would be "mydesktop.geek.lan" and "mylaptop.geek.lan".

Without knowledge of the DNS zone, a client cannot effectively query the DNS server for a "flat" name, meaning a hostname without the specified zone.

How DNS Suffixes Facilitate Resolution

The absence of a defined DNS suffix necessitates the use of the complete FQDN, such as pinging "mydesktop.geek.lan", to reach a host by its name.

However, when a DNS suffix is properly configured – either manually or through automatic configuration – the client automatically appends it to the requested hostname before querying the DNS server.

The Limitations of DNS Broadcasts

If a DNS suffix isn't defined, the client attempts to discover the name independently using a "DNS broadcast".

This method is unreliable, as not all clients are configured to respond to these broadcasts, and some may be intentionally configured to ignore them.

Consequently, consistently specifying the FQDN becomes a necessary, though inconvenient, workaround.

Key Takeaways

• Devices require a DNS suffix to automatically construct FQDNs.
• FQDNs are essential for successful DNS resolution.
• Without a DNS suffix, relying on DNS broadcasts can be problematic.

A Comprehensive DNS Solution

A complete solution to address this issue involves configuring the DNS suffix within the DHCP scope of your router. This configuration establishes a dynamic DNS server service, enabling clients to register themselves.

Furthermore, the DHCP service itself will automatically register hosts that don't self-register, and it will distribute the DNS suffix as part of the DHCP lease provided to each client. This creates a self-sustaining, default-behavior solution that resolves all related problems efficiently.

*Compatibility with routers other than DD-WRT may vary.

Configuration Steps

To implement this, navigate to the Administration page of your router:

• Access the Services menu.
• Modify the "Used Domain" setting to "LAN & WLAN".
• Select a desired domain name; "geek.lan" is used as an example, but any valid name can be chosen.
• While not mandatory, utilizing Static DHCP reservations is recommended.

If static reservations are used, ensure the hostname matches the one configured on the device's operating system. This is particularly useful for devices that don't automatically register a name in DNS, such as mobile phones, allowing you to enforce a specific hostname.

Click "Save" and then "Apply Settings" to finalize the changes.

*Note that using ".local" as the domain name may cause issues with Linux systems. These systems often adhere to the mDNS (Multicast DNS) standard and may ignore the configured DNS server. A workaround exists, but it falls outside the scope of this guide.

Verification Process

To confirm the settings have been applied correctly, open a command line interface and execute the "ipconfig" command.

Initially, the DNS suffix will likely be absent, as shown below: