DNS resolution problems

1. DNS Server Not Responding

When Pi-hole becomes unresponsive or stops working, it's typically due to the service being offline or misconfigured. To resolve this, first check Pi-hole's status using the pihole status command. If issues persist, restart the service with sudo service pihole-FTL restart.

2. Incorrect DNS Server Settings

DNS resolution problems often occur when devices aren't properly configured to use Pi-hole. Ensure Pi-hole is set as the primary DNS server either through your router's DHCP settings or by manually configuring individual devices.

3. Upstream DNS Issues

When upstream DNS servers experience downtime, it can affect Pi-hole's functionality. The solution is to configure alternative upstream DNS servers through the Pi-hole admin panel.

4. Domain Resolution Failures

If specific domains aren't resolving, this may be due to either blocklist entries or DNS cache issues. Review Pi-hole logs to identify blocked domains and whitelist necessary ones. For cache-related issues, clear your DNS cache (Windows: ipconfig /flushdns, or restart networking on other systems).

5. Local DNS Record Problems

When local DNS records fail to resolve, the issue usually stems from incorrect configuration. Verify and correct local DNS settings through Pi-hole's admin interface under the Local DNS Records section.

6. DNSSEC Validation Issues

DNSSEC validation can fail due to incorrect system time or lack of upstream provider support. Ensure your system clock is accurate, or if necessary, disable DNSSEC in Pi-hole settings when using unsupported providers.

7. Recursive DNS Problems

Query loops can occur when your router acts as a DNS forwarder. To resolve this, either disable DNS rebind protection on your router or configure Pi-hole to handle DHCP services.

8. IPv6 Configuration Issues

Problems with IPv6 DNS resolution typically indicate incorrect IPv6 configuration. Enable IPv6 in Pi-hole settings and configure the appropriate upstream IPv6 DNS servers.

9. DNS Query Latency

Slow DNS resolution may result from inefficient upstream DNS servers or network problems. Use diagnostic tools like dig to measure response times from different DNS providers and select the most efficient options.

10. Incorrect IP Resolution

When domains resolve to incorrect IP addresses, this may indicate DNS spoofing or conflicting local DNS entries. Investigate Pi-hole's DNS settings, logs, and local DNS configurations to identify and resolve any conflicts.

11. Missing Query Logs

If Pi-hole logs show no queries, devices may not be using Pi-hole for DNS resolution. Verify that Pi-hole is configured as the primary DNS server across your network and check individual device DNS settings.

For general troubleshooting, regularly monitor the Pi-hole query log and utilize the built-in diagnostic tool (pihole -d) to identify and resolve DNS resolution issues.