The answer is to re-enter the `ip name-server 192.168.1.100` command and verify with `show ip dns`. This is correct because without a specific DNS server configured, the switch defaults to sending broadcast DNS queries to 255.255.255.255, which only works if a DNS server happens to be listening on the same broadcast domain—explaining the intermittent failures. On the CCNA 200-301 v2 exam, this scenario tests your understanding of DNS client configuration and the critical distinction between directed and broadcast name resolution. A common trap is assuming a DNS server is automatically discovered; in reality, Cisco devices require an explicit `ip name-server` entry to send unicast queries. Always verify with `show ip dns` to confirm the server is listed. Memory tip: "No server, no direction—broadcasts are a guess, unicasts are a success."
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. 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.
Network Topology
You are connected to R1, a multilayer switch acting as a DNS client for internal name resolution. The network uses a private DNS server at 192.168.1.100. Users report that resolving the hostname 'server01.courseiva.local' fails intermittently. Diagnose and fix the DNS resolution issue by examining the current configuration and using appropriate show commands to verify.
R1#show running-config | section ip domain
ip domain lookup
ip domain name courseiva.local
ip name-server 192.168.1.100
!
R1#show ip dns
No DNS servers configured
R1#ping 192.168.1.100
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5)
R1#nslookup server01.courseiva.local
Translating "server01.courseiva.local"...domain server (255.255.255.255)
% Unrecognized host or address, or protocol not running.
A
Re-enter the 'ip name-server 192.168.1.100' command and verify with 'show ip dns'.
The 'ip name-server' command is missing from the running configuration, causing the switch to send DNS queries to the broadcast address instead of the specific DNS server. Re-entering the command and verifying with 'show ip dns' ensures the DNS server is properly configured.
B
Configure 'ip domain lookup' to enable DNS resolution on the switch.
Why wrong: This is incorrect because 'ip domain lookup' is already enabled; the issue is the missing name-server entry, not the lookup feature itself.
C
Change the 'ip domain name' to 'courseiva.local' to match the hostname being resolved.
Why wrong: This is incorrect because the 'ip domain name' is already set correctly to 'courseiva.local'. The issue is not the domain name but the missing name-server entry.
D
Use 'debug ip dns' to monitor DNS queries and identify the problem.
Why wrong: This is incorrect because while debugging can help identify issues, it does not fix the missing name-server configuration. The root cause is the empty name-server list, which requires re-entering the command.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Re-enter the 'ip name-server 192.168.1.100' command and verify with 'show ip dns'.
The 'ip name-server' command was missing from the configuration, causing the switch to use broadcast DNS queries (to 255.255.255.255) instead of a specific server. Broadcast queries may occasionally succeed if a DNS server on the network answers them, producing the reported intermittent failures. Re-entering the 'ip name-server 192.168.1.100' command forces directed queries, ensuring reliable resolution. After configuration, a 'ping server01.courseiva.local' will trigger DNS and confirm success if the server is reachable.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Re-enter the 'ip name-server 192.168.1.100' command and verify with 'show ip dns'.
Why this is correct
The 'ip name-server' command is missing from the running configuration, causing the switch to send DNS queries to the broadcast address instead of the specific DNS server. Re-entering the command and verifying with 'show ip dns' ensures the DNS server is properly configured.
Configure 'ip domain lookup' to enable DNS resolution on the switch.
Why it's wrong here
This is incorrect because 'ip domain lookup' is already enabled; the issue is the missing name-server entry, not the lookup feature itself.
✗
Change the 'ip domain name' to 'courseiva.local' to match the hostname being resolved.
Why it's wrong here
This is incorrect because the 'ip domain name' is already set correctly to 'courseiva.local'. The issue is not the domain name but the missing name-server entry.
✗
Use 'debug ip dns' to monitor DNS queries and identify the problem.
Why it's wrong here
This is incorrect because while debugging can help identify issues, it does not fix the missing name-server configuration. The root cause is the empty name-server list, which requires re-entering the command.
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.
✓Re-enter the 'ip name-server 192.168.1.100' command and verify with 'show ip dns'.Correct answer▾
Why this is correct
The 'ip name-server' command is missing from the running configuration, causing the switch to send DNS queries to the broadcast address instead of the specific DNS server. Re-entering the command and verifying with 'show ip dns' ensures the DNS server is properly configured.
✗Configure 'ip domain lookup' to enable DNS resolution on the switch.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that 'ip domain lookup' enables DNS client functionality but does not specify which DNS server to use. The command is already present, so reconfiguring it does not fix the missing server IP.
Why candidates choose this
Candidates might assume DNS resolution is completely disabled and that enabling it will solve the problem, overlooking that the server list is empty.
✗Change the 'ip domain name' to 'courseiva.local' to match the hostname being resolved.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the domain name is already configured correctly; changing it would not address the empty name-server list.
Why candidates choose this
Candidates may think the domain name is missing or incorrect, especially if they see 'server01' without the domain in the hostname, but the domain is already set.
✗Use 'debug ip dns' to monitor DNS queries and identify the problem.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that debugging is a diagnostic tool, not a corrective action. The question asks to 'fix' the issue, not just diagnose it.
Why candidates choose this
Candidates might think debugging will reveal the problem and then they can fix it, but the question expects a direct fix. Debugging alone does not resolve the missing configuration.
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: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Trap categories for this question
Command / output trap
This is incorrect because while debugging can help identify issues, it does not fix the missing name-server configuration. The root cause is the empty name-server list, which requires re-entering the command.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
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 block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 200-301 subnetting questions on CIDR, address ranges, and subnet selection.
Network Services and Security — This question tests Network Services and Security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Re-enter the 'ip name-server 192.168.1.100' command and verify with 'show ip dns'. — The 'ip name-server' command was missing from the configuration, causing the switch to use broadcast DNS queries (to 255.255.255.255) instead of a specific server. Broadcast queries may occasionally succeed if a DNS server on the network answers them, producing the reported intermittent failures. Re-entering the 'ip name-server 192.168.1.100' command forces directed queries, ensuring reliable resolution. After configuration, a 'ping server01.courseiva.local' will trigger DNS and confirm success if the server is reachable.
What should I do if I get this 200-301 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 200-301 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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