N10-009 Networking Concepts Practice Question
A network technician is troubleshooting a workstation that can reach devices on its local subnet but cannot access any hosts on remote networks. The technician runs ipconfig and sees that the workstation has a valid IP address and subnet mask but no default gateway configured. Which of the following best describes why the missing default gateway causes this behavior?
⚠ Common exam trap
The trap here is assuming the default gateway performs name resolution or address assignment, when it is actually the next-hop router for off-subnet traffic.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The default gateway forwards traffic to remote networks when the destination is outside the local subnet.
A host uses its configured default gateway to reach any destination outside its own subnet. When the gateway is missing, the host can still communicate locally because local traffic is delivered directly via ARP and Layer 2, but it has no next hop for remote networks, so those connections fail. The other functions listed belong to DHCP, DNS, or general router behavior, not to the gateway role.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The default gateway forwards traffic to remote networks when the destination is outside the local subnet.
Why this is correct
The default gateway is the router interface that a host uses when the destination IP address is not on its own subnet. Without it, the host has no way to send packets beyond the local broadcast domain, so remote hosts are unreachable even though local communication still works. This directly explains the observed symptom.
- ✗
The default gateway filters broadcast traffic to prevent loops within the local subnet.
Why it's wrong here
Routers do not forward broadcasts, but that is a general property of routing, not the purpose of a default gateway. The default gateway is specifically the next-hop address for off-subnet destinations. Filtering broadcasts would not explain why remote unicast traffic fails while local traffic succeeds.
- ✗
The default gateway resolves hostnames to IP addresses for remote connections.
Why it's wrong here
Hostname resolution is performed by DNS servers, not by the default gateway. The gateway operates at Layer 3 to route packets. A missing gateway would not prevent name resolution if DNS were configured, and the scenario describes a routing problem, not a name-resolution problem.
- ✗
The default gateway assigns IP addresses to hosts on the local subnet via DHCP.
Why it's wrong here
DHCP servers, not default gateways, assign IP addresses. A default gateway is a router address used for forwarding off-subnet traffic. In this scenario, the workstation already has a valid IP address and subnet mask, so DHCP is not the missing piece causing the remote-access failure.
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Related to this question
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Encapsulation and PDU at Each OSI Layer
Key term
DNS
DNS is the system that translates human-friendly domain names like example.com into machine-readable IP addresses so computers can find each other on a network.
Key term
ARP
Address Resolution Protocol (ARP) is a network protocol used to map a device's IP address to its physical MAC address so data can be delivered correctly on a local network.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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