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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DNS Configuration for IONOS VPS (Ubuntu Server)

This How-TO provides a complete, correct, and IONOS‑proof guide on how to enforce Cloudflare DNS (1.1.1.1 / 1.0.0.1) on an IONOS VPS running Ubuntu Server, while keeping the public IP address and gateway assigned via DHCP.

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🧠 IONOS VPS Specifics

🔹 DNS Servers Assigned via DHCP

During installation or at boot time, you may see DNS servers such as:

212.227.123.16
212.227.123.17

✔️ Official IONOS / 1&1 DNS servers
✔️ Assigned via DHCP
❌ NOT mandatory

IONOS:

• does not enforce DNS at firewall level
• does not block custom DNS resolvers
• does not overwrite systemd-networkd configurations

➡️ This makes IONOS an excellent provider for advanced network hardening.

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🏗️ Typical IONOS VPS Network Stack (Ubuntu Server)

On Ubuntu Server, IONOS almost always uses:

• ✅ systemd-networkd
• ✅ systemd-resolved
• ❌ NetworkManager (not installed)

⚠️ DHCP is mandatory for:

• Public IP address
• Default gateway
• Routing

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🎯 Goal

• Use Cloudflare as the only DNS resolver
• Ignore DNS servers received via DHCP
• Keep DHCP enabled for IP and gateway
• Ensure a persistent, reboot‑safe configuration
• Avoid any networking issues on IONOS VPS

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📁 Correct Configuration File

Correct file path:

/etc/systemd/network/10-ens6.network

✏️ Exact vi Command

sudo vi /etc/systemd/network/10-ens6.network

Full File Content

[Match]
Name=ens6

[Network]
DHCP=yes
DNS=1.1.1.1
DNS=1.0.0.1
Domains=~.

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✅ Effective Result on IONOS

• Public IP → assigned by DHCP (IONOS)
• Gateway → assigned by DHCP (IONOS)
• DNS → Cloudflare only
• IONOS DNS → ❌ ignored
• Reboot → ✅ safe
• DHCP renew → ✅ safe

IONOS does not overwrite this configuration.

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🔍 What Happens at Boot

1. VPS starts
2. systemd-networkd activates interface ens6
3. DHCP assigns IP address and gateway
4. DHCP DNS servers are received but discarded
5. systemd-resolved uses:

1.1.1.1 → primary
1.0.0.1 → fallback

✔️ No silent fallback to ISP DNS

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🔄 Apply the Configuration

sudo systemctl restart systemd-networkd
sudo systemctl restart systemd-resolved

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🧪 IONOS‑Proof Verification

Check Active DNS Resolver

resolvectl query ionos.com

resolvectl status

Expected output:

-- link: ens6
-- server: 1.1.1.1

Expected output:

Global
         Protocols: -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
  resolv.conf mode: stub
Current DNS Server: 1.1.1.1
       DNS Servers: 1.1.1.1 208.67.222.222

Link 2 (ens6)
    Current Scopes: DNS
         Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 1.1.1.1
       DNS Servers: 1.1.1.1 1.0.0.1 212.227.123.16 212.227.123.17
        DNS Domain: ~.

Verify Actual DNS Traffic

sudo tcpdump -i ens6 port 53

✔️ Destination ≠ 212.227. → OK*

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🔐 Recommended Hardening (PRO Level)

🔹 DNS‑over‑TLS (Cloudflare)

Edit the file:

sudo vi /etc/systemd/resolved.conf

Add or modify:

[Resolve]
DNSOverTLS=yes
DNSSEC=no

Apply changes:

sudo systemctl restart systemd-resolved

✔️ Encrypted DNS traffic
✔️ No ISP inspection

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🔹 Block Unauthorized DNS (nftables)

sudo nft add rule inet filter output udp dport 53 ip daddr != 1.1.1.1 drop
sudo nft add rule inet filter output tcp dport 53 ip daddr != 1.1.1.1 drop

✔️ Fully allowed on IONOS
✔️ Prevents DNS leaks

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⚠️ What NOT to Do on IONOS

❌ Install NetworkManager
❌ Manually edit /etc/resolv.conf
❌ Configure static IPs without recovery console access

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✅ Conclusion

This configuration is:

• ✔️ 100% IONOS‑compatible
• ✔️ Clean
• ✔️ Secure
• ✔️ Persistent
• ✔️ Production‑grade

👉 Ideal DNS configuration for hardened IONOS VPS environments.