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Scenario: Internet funktioniert nicht

This checklist is for a simple support situation: a user says the internet is not working.

The goal is not to fix everything immediately. The goal is to find out where the problem probably is.

1. Ask One Clarifying Question

Does the problem happen on one device or on multiple devices?

  • One device: likely device, Wi-Fi, cable, IP configuration or DNS setting
  • Multiple devices: likely router, provider, Wi-Fi access point or local network issue

2. Check Obvious Things First

  • Wi-Fi or Ethernet connected?
  • Airplane mode disabled?
  • Router powered on?
  • Correct Wi-Fi network selected?
  • Cable fully connected?
  • Does another website fail too?

German practice:

Ich prüfe zuerst die einfachen Ursachen: WLAN, Kabel, Router und ob das Problem nur ein Gerät betrifft.

3. Check IP Configuration

Useful commands:

ipconfig        # Windows
ifconfig        # macOS/Linux
ip addr         # Linux

Look for:

  • IP address
  • subnet mask
  • default gateway
  • DNS server

Warning signs:

  • no IP address
  • 169.254.x.x address
  • missing gateway
  • missing DNS server

4. Test the Local Gateway

Example:

ping 192.168.1.1

If the gateway does not answer, the problem is probably local:

  • wrong Wi-Fi
  • weak Wi-Fi signal
  • cable issue
  • router issue
  • wrong IP range
  • DHCP problem

5. Test Internet by IP

Example:

ping 8.8.8.8

If this works, basic internet connectivity is probably available.

If this does not work, the problem may be routing, router, provider or firewall related.

6. Test DNS

Examples:

nslookup google.com
dig google.com

If ping 8.8.8.8 works but google.com does not resolve, DNS is a strong suspect.

German practice:

Die Verbindung per IP funktioniert, aber der Domainname wird nicht aufgelöst. Deshalb prüfe ich DNS.

7. Check the Route

Examples:

traceroute google.com   # macOS/Linux
tracert google.com      # Windows

This shows where packets stop on the way to the destination.

Short Decision Flow

Only one device affected?
-> Check Wi-Fi/cable/IP/DNS on that device.

All devices affected?
-> Check router, provider status and local network.

IP ping works but domain does not?
-> Check DNS.

Gateway ping fails?
-> Check local network first.