DHCP, DNS, and Default Gateway Explained for Beginners

When a user says “I am connected but there is no internet,” three terms often matter: DHCP, DNS, and default gateway. These are basic networking concepts that show up constantly in IT support.

IP address

An IP address identifies a device on a network. A normal home or office IP might look like 192.168.1.25 or 10.0.10.50.

If the address starts with 169.254, the device likely did not receive normal DHCP settings.

Subnet basics

A subnet is a smaller network range. Devices in the same subnet can usually communicate locally. The subnet mask helps define which addresses are local and which need to go through a router.

Beginner-friendly version: subnetting decides who is “in the same neighborhood” on the network.

DHCP

DHCP automatically gives devices their network settings. It usually provides:

• IP address.
• Subnet mask.
• Default gateway.
• DNS servers.

Without DHCP, users may get APIPA addresses or no usable network settings.

DNS

DNS translates names into IP addresses. For example, DNS helps turn a website name into the server address the computer needs.

If DNS is broken, the internet may seem down even when the network path works.

Default gateway

The default gateway is the router a device uses to reach other networks, including the internet.

If the gateway is missing or wrong, the device may talk to local devices but fail to reach outside resources. Cantonese-friendly: “Default gateway 好似出口，冇出口就出唔到外面 network.”

How this relates to connected but no internet

Connected Wi-Fi or Ethernet only means the device has a link. It still needs correct IP settings.

Common patterns:

• 169.254.x.x address: likely DHCP problem.
• Valid IP but no gateway: gateway assignment problem.
• Can ping gateway but not websites: could be DNS or internet routing.
• Can ping public IP but not domain names: likely DNS.

Beginner troubleshooting commands

Use these commands carefully:

• ipconfig shows IP address, subnet mask, gateway, and basic adapter info.
• ipconfig /all shows DHCP server, DNS servers, and more detail.
• ping <gateway> tests local gateway reachability.
• ping 8.8.8.8 can test basic outside IP reachability where allowed.
• nslookup example tests DNS resolution using a domain your workplace allows.

Step-by-step support flow

1. Check whether the issue affects one device or many.
2. Run ipconfig /all.
3. Confirm IP address, subnet mask, default gateway, and DNS.
4. Ping the gateway.
5. Test DNS with nslookup.
6. Compare with a working device on the same network.
7. Escalate to network support if multiple users or VLAN/DHCP scope issues appear.

Beginner Note

Do not jump straight to changing DNS. First check whether the device has a valid IP address and gateway.

Common Mistake

A common mistake is seeing “connected” and assuming the network is fine. Connected only proves the cable or Wi-Fi association exists. It does not prove DHCP, DNS, gateway, or routing works.

Help desk example

A laptop connects to Wi-Fi but cannot browse. ipconfig shows 169.254.22.10. That points toward DHCP reachability, not a browser issue.

FAQ

Is DNS the same as the default gateway?

No. DNS resolves names. The default gateway routes traffic outside the local network.

Can internet fail if DNS is wrong?

Yes. Users may not open websites by name, even if the network path is working.

What does DHCP failure look like?

Often a 169.254 IP address, missing gateway, or no usable network configuration.

Should I memorize every subnet rule first?

No. Start by recognizing local IP settings, gateway, DHCP, and DNS. Deeper subnetting can come later.