DNS Resolver Testing with Python: Compare Performance, Test DNSSEC, and Diagnose Issues (Free CLI Tool)

DNS resolution is the first step in every network connection, and slow or unreliable DNS causes cascading latency across your entire infrastructure. Whether you are choosing between public resolvers like Cloudflare (1.1.1.1), Google (8.8.8.8), and Quad9 (9.9.9.9), or diagnosing resolution failures, you need objective measurement.

dargslan-dns-resolver is a free Python CLI tool that tests DNS resolver performance, compares multiple resolvers, checks DNSSEC validation, and audits your resolver configuration.

Quick Start

pip install dargslan-dns-resolver

dargslan-dns report                      # Full DNS report
dargslan-dns resolve dargslan.com        # Quick resolution test
dargslan-dns compare 8.8.8.8 1.1.1.1    # Compare resolver speeds
dargslan-dns dnssec google.com           # DNSSEC validation test
dargslan-dns reverse 8.8.8.8             # Reverse DNS lookup
dargslan-dns config                      # Show resolver configuration

Resolver Performance Comparison

The compare command benchmarks multiple DNS resolvers against a set of popular domains. It runs multiple rounds and reports average, minimum, and maximum query times. This gives you objective data for choosing the fastest resolver for your location and network.

DNSSEC Verification

DNSSEC (DNS Security Extensions) protects against DNS spoofing by cryptographically signing DNS records. The tool checks whether a domain has DNSSEC signatures and whether your resolver properly validates them (indicated by the AD flag in the response).

Python API

from dargslan_dns_resolver import DNSResolver

dr = DNSResolver()
resolvers = dr.get_system_resolvers()
for r in resolvers:
    print(f"Resolver: {r['ip']} {r.get('name', '')}")

result = dr.resolve("dargslan.com")
print(f"Resolved in {result['time_ms']}ms: {result['results']}")

for comp in dr.compare_resolvers(["8.8.8.8", "1.1.1.1", "9.9.9.9"]):
    print(f"{comp['server']}: avg={comp['avg_ms']}ms")

Diagnosing DNS Issues

• No resolvers configured: Check /etc/resolv.conf for nameserver entries
• Slow resolution: Compare with public resolvers to isolate the issue
• Resolution failures: Test with dig directly to check whether the resolver or network is the problem
• Single resolver: Always configure at least two resolvers for redundancy

Best Practices

1. Configure at least two DNS resolvers for redundancy
2. Test resolver performance periodically — network conditions change
3. Enable DNSSEC validation on your resolvers
4. Monitor DNS resolution latency as part of your observability stack
5. Use the closest resolver geographically for minimum latency

Conclusion

DNS performance directly impacts every service on your network. dargslan-dns-resolver gives you the tools to test, compare, and optimize your DNS configuration. Install it and make DNS performance part of your monitoring.

For more infrastructure tools, visit dargslan.com.