Resolve the Frustrating DNS Loop: Fix systemd-resolved with Stub Listener on Port 53

May 10, 2025

Fixing systemd-resolved Looping DNS Queries with Stub Listener

In today’s digital landscape, efficient DNS resolution is crucial for maintaining network performance and reliability. systemd-resolved is a system service that provides network name resolution to local applications. However, misconfigurations can lead to looping DNS queries, causing significant disruptions. This guide will walk you through the steps to fix these issues by configuring the stub listener effectively, ensuring your DNS queries are resolved correctly and efficiently.

Understanding the Problem

Looping DNS queries occur when a DNS resolver continuously queries itself for a resolution, leading to increased latency and potential service outages. This issue is often caused by incorrect configurations in the systemd-resolved service or conflicts with other DNS services. Addressing this problem is essential for maintaining a stable network environment.

Configuration Steps

Step 1: Check Current systemd-resolved Status

Before making any changes, it’s important to check the current status of systemd-resolved. Use the following command:

systemctl status systemd-resolved

This command will provide information about whether the service is active and any potential errors in its operation.

Step 2: Verify DNS Configuration

Next, verify the current DNS configuration by checking the resolved configuration file:

cat /etc/systemd/resolved.conf

Look for the following parameters:

DNS: The DNS servers that are currently configured.
FallbackDNS: The fallback DNS servers.
Domains: The search domains.

Step 3: Configure the Stub Listener

To fix looping DNS queries, ensure that the stub listener is enabled. Open the resolved configuration file for editing:

sudo nano /etc/systemd/resolved.conf

Make sure the following line is present and uncommented:

DNSStubListener=yes

This setting allows systemd-resolved to listen on the local loopback interface (127.0.0.53) for DNS queries.

Step 4: Restart systemd-resolved

After making changes, restart the systemd-resolved service to apply the new configuration:

sudo systemctl restart systemd-resolved

Step 5: Test DNS Resolution

Finally, test the DNS resolution to ensure that the changes have resolved the looping queries. Use the following command:

dig @127.0.0.53 example.com

Replace example.com with a domain of your choice. Check the output for any errors or indications of looping queries.

Practical Examples

Consider a scenario where a server is configured to use an external DNS service, but due to misconfiguration, it ends up querying itself. By following the steps outlined above, you can redirect the queries correctly and avoid unnecessary loops.

Best Practices

Regularly monitor the status of systemd-resolved to catch issues early.
Keep your system and packages updated to benefit from the latest fixes and improvements.
Document any changes made to the DNS configuration for future reference.

Case Studies and Statistics

According to a study by the Internet Systems Consortium, misconfigured DNS settings account for approximately 30% of network-related issues in enterprise environments. By implementing best practices and ensuring proper configuration of systemd-resolved, organizations can significantly reduce downtime and improve overall network performance.

Conclusion

Fixing looping DNS queries with systemd-resolved is a critical task for maintaining network stability. By following the steps outlined in this guide, you can effectively configure the stub listener and ensure efficient DNS resolution. Remember to regularly monitor your DNS settings and adhere to best practices to prevent future issues. With these actionable insights, you can enhance your network’s performance and reliability.