dnsperftest

A DNS load testing tool that fires concurrent queries at a DNS server and reports performance stats. Built to stress-test Pi-hole, dnscrypt-proxy, or any DNS resolver.

Single-file .NET 10 app — no dependencies, no project file.

Requirements

• .NET 10 SDK

Usage

dotnet run dnsperftest.cs -- --server <ip-or-hostname> [options]

Options

Flag	Short	Default	Description
--server	-s	required	DNS server IP or hostname
--requests	-n	1000	Total number of queries to send
--concurrency	-c	50	Max concurrent queries in flight
--timeout	-t	2000	Per-query timeout in milliseconds
--random	-r	off	Prepend random subdomain to bypass DNS cache

Examples

# Test your Pi-hole with defaults (1000 requests, 50 concurrent)
dotnet run dnsperftest.cs -- -s pi.hole

# Stress test with high concurrency
dotnet run dnsperftest.cs -- -s 192.168.1.10 -n 5000 -c 200

# Test uncached performance (bypasses DNS cache)
dotnet run dnsperftest.cs -- -s pi.hole -n 1000 -c 50 --random

# Test against Google DNS
dotnet run dnsperftest.cs -- -s 8.8.8.8 -n 500 -c 20

Output

DNS Performance Test
  Server:      pi.hole
  Requests:    1000
  Concurrency: 50
  Timeout:     2000ms

Results:
  Successful:  1000
  Failed:      0 (0.0%)
  Total time:  0.13s
  Req/sec:     7598.7
  Latency (ms):
    Min:       0.7
    Avg:       5.5
    P50:       4.7
    P95:       9.9
    P99:       13.3
    Max:       13.9

How it works

• Sends raw UDP DNS A-record queries directly to the target server (bypasses OS resolver cache)
• Uses SemaphoreSlim to cap concurrency
• Rotates through 20 built-in popular domains
• With --random, prepends a unique GUID subdomain to each query to force cache misses
• NXDOMAIN responses count as successful (the server did its job)