DNS Speed Test Script.md

DNS Speed Test Script

A simple Bash script to measure and compare DNS query response times from popular public DNS servers.
Outputs aligned ASCII tables showing raw and sorted results by speed.

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Tested Environment

This script has been tested on the following Linux distribution:

• Distributor ID: Ubuntu
• Description: Ubuntu 22.04.5 LTS
• Release: 22.04
• Codename: jammy

Note: On this system, /etc/resolv.conf is a symbolic link to /run/systemd/resolve/stub-resolv.conf.

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Features

• Tests multiple well-known DNS servers (Cloudflare, Google, Quad9, OpenDNS, AdGuard, ControlD)
• Measures query time to resolve a specified domain (default: example.com)
• Handles no-response cases gracefully by marking them as NO RESP
• Outputs two clean, ASCII-aligned tables:
  • Original unsorted results
  • Results sorted from fastest to slowest
• Fully ASCII-safe with dynamic column width adjustment

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DNS Servers Tested

• Cloudflare (1.1.1.1)
• Google Primary (8.8.8.8)
• Google Backup (8.8.4.4)
• Quad9 (9.9.9.9)
• OpenDNS Primary (208.67.222.222)
• OpenDNS Backup (208.67.220.220)
• AdGuard Primary (94.140.14.14)
• AdGuard Backup (94.140.15.15)
• ControlD Primary (76.76.2.0)
• ControlD Backup (76.76.10.0)

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Usage

./dns-speed-test.sh [domain]

• domain — Optional. The domain to resolve. Defaults to example.com if omitted.

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Download Script

You can download the latest version of the DNS Speed Test script from GitHub:

Download dns-speed-test.sh

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Example Output

+-----------+-------------+--------+
| Name      | IP          |  Time  |
+-----------+-------------+--------+
| Cloudflare| 1.1.1.1     |    12ms|
| Google    | 8.8.8.8     |    14ms|
| Quad9     | 9.9.9.9     | NO RESP|
+-----------+-------------+--------+

Sorted (from fastest to slowest):
+-----------+-------------+--------+
| Name      | IP          |  Time  |
+-----------+-------------+--------+
| Cloudflare| 1.1.1.1     |    12ms|
| Google    | 8.8.8.8     |    14ms|
| Quad9     | 9.9.9.9     | NO RESP|
+-----------+-------------+--------+

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How It Works

• Uses dig to query each DNS server for the provided domain.
• Extracts the query time from the dig output.
• If no response is received within the timeout, marks it as NO RESP with a high sort value to appear last.
• Prints two tables:
  1. The original order of DNS servers tested
  2. Sorted results by ascending query time

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Dependencies

• bash
• dig (from bind-utils or dnsutils package)

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License

MIT License

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Note: To convert a text file from DOS/Windows format (CRLF line endings) to Linux/Unix format (LF line endings), you can use the following sed command:

sed -i 's/\r$//' filename

This command removes the carriage return character (\r) at the end of each line, converting the file to Unix-style line endings.

Alternatively, if available, the dos2unix tool can be used for a straightforward conversion:

dos2unix filename

DNS Configuration Note for systemd-resolved

Note:
If you want to modify DNS settings, keep in mind that the file /run/systemd/resolve/resolv.conf is managed dynamically by systemd-resolved and should not be edited directly. Instead, you should modify the configuration file:

/etc/systemd/resolved.conf

For example, add or modify the [Resolve] section like this:

#  This file is part of systemd.
#
#  systemd is free software; you can redistribute it and/or modify it under the
#  terms of the GNU Lesser General Public License as published by the Free
#  Software Foundation; either version 2.1 of the License, or (at your option)
#  any later version.
#
# Entries in this file show the compile time defaults. Local configuration
# should be created by either modifying this file, or by creating "drop-ins" in
# the resolved.conf.d/ subdirectory. The latter is generally recommended.
# Defaults can be restored by simply deleting this file and all drop-ins.
#
# Use 'systemd-analyze cat-config systemd/resolved.conf' to display the full config.
#
# See resolved.conf(5) for details.

[Resolve]
# Some examples of DNS servers which may be used for DNS= and FallbackDNS=:
# Cloudflare: 1.1.1.1#cloudflare-dns.com 1.0.0.1#cloudflare-dns.com 2606:4700:4700::1111#cloudflare-dns.com 2606:4700:4700::1001#cloudflare-dns.com
# Google:     8.8.8.8#dns.google 8.8.4.4#dns.google 2001:4860:4860::8888#dns.google 2001:4860:4860::8844#dns.google
# Quad9:      9.9.9.9#dns.quad9.net 149.112.112.112#dns.quad9.net 2620:fe::fe#dns.quad9.net 2620:fe::9#dns.quad9.net
#DNS=
DNS=1.1.1.1 208.67.222.222
#FallbackDNS=
#Domains=
#DNSSEC=no
#DNSOverTLS=no
#MulticastDNS=no
#LLMNR=no
#Cache=no-negative
#CacheFromLocalhost=no
#DNSStubListener=yes
#DNSStubListenerExtra=
#ReadEtcHosts=yes
#ResolveUnicastSingleLabel=no

After saving the changes, restart the service with:

sudo systemctl restart systemd-resolved.service

To verify that the DNS servers are correctly applied, run:

resolvectl status