CCNA Network Services and Security Practice Question
Exhibit
Client IP address: 192.168.50.23/24 Ping to 192.168.50.1 succeeds Ping to 8.8.8.8 fails DHCP pool intended for VLAN 50 users
A client receives an IP address but cannot reach remote networks. Which DHCP option is most likely missing or incorrect?
⚠ Common exam trap
Cisco often tests the distinction between DHCP options by presenting a symptom like 'can't reach the internet' and expecting candidates to recognize that the default gateway (option 3) is the critical missing piece, not DNS or lease time.
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
✓
Default gateway option
The client can obtain an IP address but cannot reach remote networks, which indicates that the DHCP server is not providing the default gateway (option 3). Without a default gateway, the client has no route to destinations outside its local subnet, so traffic to remote networks is dropped. The DHCP server must be configured to supply the router's IP address as the default gateway for clients to forward inter-network traffic.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
DNS server option
Why it's wrong here
The DNS Server option provides the client with the IP addresses of name servers used to resolve hostnames to IP addresses. If this option is wrong, the client can still exchange IP packets with remote networks by typing an IP address directly, but it will fail to resolve DNS names. It does not affect the forwarding path or the default gateway's operation.
When this WOULD be correct
In a different scenario where the question specifies that clients can access local resources but fail to resolve domain names, the DNS server option would be the correct answer. For example, if the client can ping local IPs but not external domains, the DNS configuration would be the likely issue.
- ✗
Lease time option
Why it's wrong here
Lease time is the DHCP option that defines how long the client can use the assigned IP address before it must renew its lease. It controls address expiration and renewal timing, but has no influence on the client's routing table or its ability to reach remote subnets. Even a very short lease time does not block off-subnet traffic while the address is valid.
When this WOULD be correct
In a different scenario, if a question asks about DHCP configurations affecting client connectivity specifically related to lease durations, a missing lease time option could lead to clients not being able to renew their IP addresses, thus causing connectivity issues.
- ✓
Default gateway option
Why this is correct
The DHCP 'Default Gateway' option (router option) supplies the client with the IP address of the local router that provides exit from the subnet. Without a correct gateway address, the client does not know where to forward packets destined for non-local networks, so it attempts to ARP for the destination address directly and ultimately drops the traffic. This is why an incorrect or missing gateway prevents all off-subnet communication.
- ✗
TFTP server option
Why it's wrong here
The TFTP Server option is typically used for network booting, such as Cisco IP phones or diskless workstations, to download configuration files or operating system images. For an ordinary client PC, a TFTP server has no role in basic IP connectivity, and the client does not require TFTP to route traffic to remote networks. Misconfiguring this option will not interfere with the client's ability to communicate outside its subnet.
When this WOULD be correct
In a scenario where a question asks about a client that can reach local resources but cannot download files from a remote server, the TFTP server option could be missing or incorrectly configured. This would directly affect the client's ability to access TFTP services, making this option correct in that context.
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.
✓Default gateway optionCorrect answer▾
Why this is correct
The DHCP 'Default Gateway' option (router option) supplies the client with the IP address of the local router that provides exit from the subnet. Without a correct gateway address, the client does not know where to forward packets destined for non-local networks, so it attempts to ARP for the destination address directly and ultimately drops the traffic. This is why an incorrect or missing gateway prevents all off-subnet communication.
✗DNS server optionWrong answer — click to see why▾
Why this is wrong here
The DNS server option is not critical for basic connectivity to remote networks; it primarily affects name resolution. If a client can obtain an IP address but cannot reach remote networks, the issue is more likely related to the default gateway configuration.
★ When this WOULD be the correct answer
In a different scenario where the question specifies that clients can access local resources but fail to resolve domain names, the DNS server option would be the correct answer. For example, if the client can ping local IPs but not external domains, the DNS configuration would be the likely issue.
Why candidates choose this
Candidates may choose this option because they associate DNS with network connectivity issues, especially if they have encountered problems where name resolution failures caused access issues. This can lead to confusion about the role of DNS in overall network functionality.
✗Lease time optionWrong answer — click to see why▾
Why this is wrong here
The lease time option specifies how long a DHCP lease is valid, but it does not affect the ability to reach remote networks. Therefore, a missing or incorrect lease time would not directly cause connectivity issues.
★ When this WOULD be the correct answer
In a different scenario, if a question asks about DHCP configurations affecting client connectivity specifically related to lease durations, a missing lease time option could lead to clients not being able to renew their IP addresses, thus causing connectivity issues.
Why candidates choose this
Candidates may confuse the lease time option with overall network connectivity, thinking that if a client cannot reach remote networks, it could be due to lease issues rather than routing configurations.
✗TFTP server optionWrong answer — click to see why▾
Why this is wrong here
The TFTP server option is not necessary for a client to reach remote networks, as it primarily facilitates file transfers and does not impact routing or network accessibility. Therefore, its absence would not directly cause connectivity issues to remote networks.
★ When this WOULD be the correct answer
In a scenario where a question asks about a client that can reach local resources but cannot download files from a remote server, the TFTP server option could be missing or incorrectly configured. This would directly affect the client's ability to access TFTP services, making this option correct in that context.
Why candidates choose this
Candidates may be tempted by this option because TFTP is often associated with network services and can seem relevant when discussing connectivity issues, leading them to mistakenly believe it could impact overall network access.
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?”
Visual reference
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Related to this question
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Device File Management with SFTP and SCP
Key term
Router
A router is a networking device that connects different networks together and directs data traffic between them by choosing the best path for data to travel.
Key term
CAN
A CAN (Controller Area Network) is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other without a host computer.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.