What Is a Default Gateway? (Explained Simply)
The default gateway is one of the most important networking concepts on the CompTIA A+ exam.
It is the device that allows your computer to communicate outside its local network.
Simple Definition
A default gateway is the router your device sends traffic to when it needs to reach another network (like the internet).
Think of it as the “exit door” of your network.
Example
Your computer:
- IP Address: 192.168.1.25
- Subnet Mask: 255.255.255.0
- Default Gateway: 192.168.1.1
If you try to visit Google, your computer sends the request to 192.168.1.1 (your router).
The router then forwards the request to the internet.
When Is the Default Gateway Used?
- When communicating outside your subnet
- When accessing the internet
- When reaching another network
If traffic is within your local network, the gateway is not needed.
How It Appears on the A+ Exam
Exam questions may ask:
- Why can a device reach local computers but not the internet?
- What setting is missing if internet access fails?
The answer is often:
Incorrect or missing default gateway.
Troubleshooting Example
If you run:
ipconfig
And the Default Gateway field is blank — your device cannot access the internet.
This often indicates:
- DHCP failure
- Incorrect static configuration
- Router issue
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