The answer is the DHCP DNS server option, because when clients receive a valid IP address and default gateway but cannot browse by hostname, the missing piece is almost always the DNS server information that DHCP should provide. Without the DNS server option configured in the DHCP scope, clients have no way to translate hostnames into IP addresses, so name resolution fails even though IP connectivity to destinations by direct address remains intact. On the CCNA 200-301 v2 exam, this scenario tests your understanding of how DHCP delivers more than just an address—it also supplies critical options like DNS and domain name, and a common trap is to assume the problem lies with routing or the gateway when the real issue is the missing DNS server. To remember this, think of the mnemonic “IP works, names don’t? Check the DHCP DNS option.”
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: the DHCP DNS server option provides clients with the IP address of DNS servers to enable hostname resolution on the network.. 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.
Exhibit
Client output:
IP address: 192.168.50.22/24
Default gateway: 192.168.50.1
DNS server: 0.0.0.0
Users receive addresses from the correct subnet and can reach destinations by IP address, but they cannot browse by hostname.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
DNS server option
If clients get an IP address and default gateway but cannot resolve names, the usual problem is the DNS server information handed out by DHCP. Without that, hostname lookups fail even though IP connectivity may still exist.
Key principle: The DHCPDNS server option provides clients with the IP address of DNS servers to enable hostname resolution on the network.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Default-router option
Why it's wrong here
A missing default gateway would affect off-subnet traffic, not just hostname resolution.
When this WOULD be correct
In a different scenario where users cannot access external networks or specific services, but can resolve hostnames, the Default-router option could be missing or incorrect, leading to connectivity issues outside the local subnet.
✓
DNS server option
Why this is correct
The DNS server option tells clients where to send name-resolution queries.
Related concept
The DHCPDNS server option provides clients with the IP address of DNS servers to enable hostname resolution on the network.
✗
Lease time option
Why it's wrong here
Lease duration does not determine whether DNS lookups work.
When this WOULD be correct
If the question were about a DHCP configuration issue where clients were unable to maintain their IP addresses or frequently lost connectivity, then a missing or incorrect lease time option could be the cause, making this answer correct.
✗
TFTP server option
Why it's wrong here
TFTP is used for file transfer, often by phones or booting clients.
When this WOULD be correct
In a different scenario where users are unable to download configuration files or firmware updates from a TFTP server, the question might ask which DHCP option is missing. In that case, if the TFTP server option is not provided, it would be the correct answer.
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.
✓DNS server optionCorrect answer▾
Why this is correct
The DNS server option tells clients where to send name-resolution queries.
✗Default-router optionWrong answer — click to see why▾
Why this is wrong here
The default-router option (option 3) provides the gateway for off-subnet traffic. While a missing gateway would prevent access to external networks, the scenario states users receive correct subnet addresses and can likely reach local resources. The inability to browse by hostname points to a DNS issue, not a routing problem.
★ When this WOULD be the correct answer
In a different scenario where users cannot access external networks or specific services, but can resolve hostnames, the Default-router option could be missing or incorrect, leading to connectivity issues outside the local subnet.
Why candidates choose this
Test-takers often associate internet browsing with a default gateway, assuming that if hostname resolution fails, it might be due to lack of internet connectivity. However, the question specifies that users cannot browse by hostname, which is a DNS function, not a routing one.
✗Lease time optionWrong answer — click to see why▾
Why this is wrong here
The lease time option (option 51) determines how long a client can use an assigned IP address before renewing. It does not affect DNS resolution or hostname browsing. A missing or incorrect lease time would cause IP address expiration issues, not name resolution failures.
★ When this WOULD be the correct answer
If the question were about a DHCP configuration issue where clients were unable to maintain their IP addresses or frequently lost connectivity, then a missing or incorrect lease time option could be the cause, making this answer correct.
Why candidates choose this
Students may confuse lease time with other DHCP options that affect network functionality, or they might think that a short lease could cause intermittent connectivity that impacts DNS. However, lease time is unrelated to DNS resolution.
✗TFTP server optionWrong answer — click to see why▾
Why this is wrong here
The TFTP server option (option 66) is used for booting devices like IP phones or diskless workstations to download configuration files or operating systems. It is not involved in hostname resolution. A missing TFTP server would not affect DNS lookups.
★ When this WOULD be the correct answer
In a different scenario where users are unable to download configuration files or firmware updates from a TFTP server, the question might ask which DHCP option is missing. In that case, if the TFTP server option is not provided, it would be the correct answer.
Why candidates choose this
Students may confuse TFTP with DNS because both are UDP-based services, or they might think that TFTP is needed for some name resolution process. However, TFTP has no role in DNS resolution.
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
Don't confuse general network connectivity options with DNS-specific configurations. Focus on what each DHCP option actually configures.
Detailed technical explanation
How to think about this question
Dynamic Host Configuration Protocol (DHCP) is a network management protocol used to automate the process of configuring devices on IP networks. DHCP assigns IP addresses and other network configuration parameters, such as subnet mask, default gateway, and DNS servers, to client devices. The DNS server option in DHCP is critical because it tells clients where to send DNS queries to resolve hostnames into IP addresses, enabling hostname-based browsing and communication.
When a client device receives an IP address from a DHCP server, it also receives additional options that define how it interacts with the network. The DNS server option specifically provides the IP address of one or more DNS servers. Without this option correctly configured, clients cannot resolve domain names to IP addresses, even though they have valid IP addresses and default gateways. This results in users being unable to browse websites by hostname, despite having network connectivity.
A common exam trap is to confuse the symptoms of missing DHCP options. For example, a missing default-router option affects routing beyond the local subnet but does not prevent hostname resolution. Similarly, lease time affects IP address validity but not DNS functionality. The TFTP server option is unrelated to DNS and is used mainly for device bootstrapping or phone configuration. Understanding the specific role of each DHCP option helps avoid misdiagnosis and ensures correct troubleshooting and configuration in Cisco networks.
KKey Concepts to Remember
The DHCP DNS server option provides clients with the IP address of DNS servers to enable hostname resolution on the network.
Clients with correct IP addresses and default gateways but missing DNS server information cannot resolve hostnames to IP addresses.
The default-router DHCP option specifies the gateway for off-subnet traffic but does not affect DNS resolution.
Lease time controls how long a client can use an assigned IP address but does not impact DNS query functionality.
The TFTP server option is used for device boot or configuration file transfers and does not influence DNS or hostname resolution.
DNS resolution is essential for browsing by hostname, and DHCP must supply accurate DNS server information for this to work.
In Cisco DHCP implementations, the DNS server option is configured with the 'dns-server' command under the DHCP pool.
Troubleshooting hostname resolution issues requires verifying that the DHCP server correctly provides the DNS server option.
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
The DHCP DNS server option provides clients with the IP address of DNS servers to enable hostname resolution on the network.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review the DHCP DNS server option provides clients with the IP address of DNS servers to enable hostname resolution on the network., then practise related 200-301 questions on the same topic to reinforce the concept.
Network Services and Security — This question tests Network Services and Security — The DHCP DNS server option provides clients with the IP address of DNS servers to enable hostname resolution on the network..
What is the correct answer to this question?
The correct answer is: DNS server option — If clients get an IP address and default gateway but cannot resolve names, the usual problem is the DNS server information handed out by DHCP. Without that, hostname lookups fail even though IP connectivity may still exist.
What should I do if I get this 200-301 question wrong?
Review the DHCP DNS server option provides clients with the IP address of DNS servers to enable hostname resolution on the network., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
The DHCP DNS server option provides clients with the IP address of DNS servers to enable hostname resolution on the network.
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