- A
Configure a default gateway of 10.10.10.1 and a DNS server of 10.10.10.5.
This provides both the default gateway for routing to other subnets and the DNS server for name resolution.
- B
Configure only a DNS server of 10.10.10.5.
Why wrong: This provides DNS resolution but does not allow the workstation to reach devices on other subnets because there is no default gateway.
- C
Change the subnet mask to 255.255.0.0 to allow communication across subnets.
Why wrong: Changing the subnet mask to a larger network (e.g., /16) would group many addresses into one subnet, but it does not provide a path to other subnets; it may also cause routing issues.
- D
Configure a default gateway of 10.10.20.1 and a DNS server of 10.10.10.5.
Why wrong: The default gateway 10.10.20.1 is not on the same subnet as the host (10.10.10.0/24), so the host cannot reach it directly; this configuration would fail.
Configure Default Gateway and DNS for Inter-Subnet Communication | CCNA Explained
This 200-301 practice question tests your understanding of network infrastructure and connectivity. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network administrator is configuring a new Windows workstation on a small office network that uses IPv4 addressing. The workstation must be able to communicate with devices on other subnets and resolve hostnames via a company DNS server at 10.10.10.5. The administrator has already set the IP address to 10.10.10.10 and the subnet mask to 255.255.255.0. Which additional parameter must be configured to meet both requirements?
Quick Answer
The answer is to configure a default gateway of 10.10.10.1 and a DNS server of 10.10.10.5. For inter-subnet communication, a host must have a default gateway—typically a router interface on the same subnet—to forward packets beyond the local 10.10.10.0/24 network; without it, traffic to other subnets is dropped. Additionally, hostname resolution requires a dedicated DNS server address, as the workstation does not automatically discover it from the IP configuration. On the CCNA 200-301 v2 exam, this tests your understanding of the two distinct roles: routing (default gateway) and name resolution (DNS). A common trap is assuming a DNS server can double as a gateway, but they serve separate functions—the gateway handles Layer 3 forwarding, while DNS resolves names to IPs. Remember the mnemonic: "Gateway for the getaway, DNS for the name game."
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
Configure a default gateway of 10.10.10.1 and a DNS server of 10.10.10.5.
To communicate with devices on other subnets, the workstation needs a default gateway (router) to forward traffic beyond its local subnet. The IP address 10.10.10.10 with subnet mask 255.255.255.0 places it in the 10.10.10.0/24 network, so a default gateway (e.g., 10.10.10.1) is required for inter-subnet routing. Additionally, to resolve hostnames, the DNS server address must be explicitly configured; the company DNS server is at 10.10.10.5. Option A correctly provides both parameters.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Configure a default gateway of 10.10.10.1 and a DNS server of 10.10.10.5.
Why this is correct
This provides both the default gateway for routing to other subnets and the DNS server for name resolution.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Configure only a DNS server of 10.10.10.5.
Why it's wrong here
This provides DNS resolution but does not allow the workstation to reach devices on other subnets because there is no default gateway.
- ✗
Change the subnet mask to 255.255.0.0 to allow communication across subnets.
Why it's wrong here
Changing the subnet mask to a larger network (e.g., /16) would group many addresses into one subnet, but it does not provide a path to other subnets; it may also cause routing issues.
- ✗
Configure a default gateway of 10.10.20.1 and a DNS server of 10.10.10.5.
Why it's wrong here
The default gateway 10.10.20.1 is not on the same subnet as the host (10.10.10.0/24), so the host cannot reach it directly; this configuration would fail.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Configure a default gateway of 10.10.10.1 and a DNS server of 10.10.10.5.Correct answer▾
Why this is correct
This provides both the default gateway for routing to other subnets and the DNS server for name resolution.
✗Configure only a DNS server of 10.10.10.5.Wrong answer — click to see why▾
Why this is wrong here
Without a default gateway, the workstation cannot send packets to destinations outside its own subnet (10.10.10.0/24). The DNS server alone only provides name resolution, not routing to other subnets.
Why candidates choose this
Students may think that DNS is the only missing piece because the IP and subnet mask are already set, overlooking the need for a default gateway to reach other subnets.
✗Change the subnet mask to 255.255.0.0 to allow communication across subnets.Wrong answer — click to see why▾
Why this is wrong here
Changing the subnet mask to 255.255.0.0 would expand the broadcast domain and could cause routing problems, but it does not provide a path to other subnets. The workstation still needs a default gateway to communicate with devices outside its local network.
Why candidates choose this
Some students might incorrectly believe that a larger subnet mask allows communication across subnets by including them in the same network, but this is not how routing works; it would actually break connectivity.
✗Configure a default gateway of 10.10.20.1 and a DNS server of 10.10.10.5.Wrong answer — click to see why▾
Why this is wrong here
The default gateway 10.10.20.1 is not on the same subnet as the workstation (10.10.10.0/24). For a host to reach its default gateway, the gateway must be directly reachable on the local subnet. Since 10.10.20.1 is on a different subnet, the workstation cannot send traffic to it.
Why candidates choose this
Students might think any IP can serve as a default gateway, but they must ensure it is on the same subnet. The DNS server is correct, but the gateway is misconfigured.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the requirement that a default gateway must be on the same subnet as the host; the trap here is that candidates may think a DNS server alone suffices for inter-subnet communication, or they may incorrectly assume changing the subnet mask can replace a router, or they may choose a gateway on a different subnet without realizing it is unreachable.
Detailed technical explanation
How to think about this question
The default gateway is the next-hop router for traffic destined to non-local networks; the workstation uses its subnet mask to determine if a destination is local or remote. DNS resolution uses UDP/TCP port 53, and the DNS server address must be configured in the workstation's TCP/IP settings (or via DHCP) for hostname-to-IP translation. In a small office, the default gateway is often the router's LAN interface IP, and the DNS server may be the same device or a dedicated server.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
Visual reference
Quick reference
IPv4 Address Class Summary
| Class | First Octet Range | Default Mask | Networks | Hosts per Network |
|---|---|---|---|---|
| A | 1–126 | /8 (255.0.0.0) | 126 | 16,777,214 |
| B | 128–191 | /16 (255.255.0.0) | 16,384 | 65,534 |
| C | 192–223 | /24 (255.255.255.0) | 2,097,152 | 254 |
| D | 224–239 | N/A | Multicast groups | — |
| E | 240–255 | N/A | Reserved / experimental | — |
127.x.x.x is reserved for loopback. Modern networks use CIDR (classless) rather than classful addressing.
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FAQ
Questions learners often ask
What does this 200-301 question test?
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure a default gateway of 10.10.10.1 and a DNS server of 10.10.10.5. — To communicate with devices on other subnets, the workstation needs a default gateway (router) to forward traffic beyond its local subnet. The IP address 10.10.10.10 with subnet mask 255.255.255.0 places it in the 10.10.10.0/24 network, so a default gateway (e.g., 10.10.10.1) is required for inter-subnet routing. Additionally, to resolve hostnames, the DNS server address must be explicitly configured; the company DNS server is at 10.10.10.5. Option A correctly provides both parameters.
What should I do if I get this 200-301 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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