CCNA Network Services and Security Practice Question
Network Topology
You are connected to R1 via the console. R1 is the DHCP server for the 192.168.50.0/24 LAN. Configure DHCP on R1 to assign addresses from 192.168.50.10 to 192.168.50.200, with default gateway 192.168.50.1 and DNS server 8.8.8.8. Also, configure R1 to act as a DHCP relay agent for the 10.0.0.0/30 link to reach a remote DHCP server at 203.0.113.10. Then, troubleshoot and fix a misconfiguration that causes clients on VLAN 50 to not receive IP addresses.
⚠ Common exam trap
A single 'ip dhcp excluded-address' range does not limit the DHCP pool to only the desired contiguous range; you must explicitly exclude all addresses you do not want assigned, even those at the upper end. Ensure you create multiple excluded-address ranges when the pool is not contiguous.
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
✓
[CORRECT] The DHCP pool is misconfigured: the excluded-address range covers most of the pool (192.168.50.1 through 192.168.50.200), but leaves 192.168.50.201-254 assignable, violating the requirement. The correct configuration should exclude 192.168.50.1-9 (gateway) and 192.168.50.201-254 (upper end). The 'ip helper-address' on GigabitEthernet0/0 is unnecessary because R1 itself is the DHCP server for that subnet; it should be removed. The relay agent configuration is missing on the interface facing the remote DHCP server—'ip helper-address 203.0.113.10' should be added to GigabitEthernet0/1.
The DHCP pool is misconfigured: the excluded-address range of 192.168.50.1 through 192.168.50.200 covers most of the pool, but leaves addresses 192.168.50.201 to 192.168.50.254 assignable, which violates the requirement to assign addresses only from 192.168.50.10 to 192.168.50.200. To meet the requirement, you must exclude both the lower range (192.168.50.1 to 192.168.50.9, reserving the gateway) and the upper range (192.168.50.201 to 192.168.50.254). Additionally, the 'ip helper-address' on GigabitEthernet0/0 is unnecessary because R1 itself is the DHCP server for that subnet; it should be removed. The relay agent configuration is missing on the interface facing the remote DHCP server—'ip helper-address 203.0.113.10' should be added to GigabitEthernet0/1 so that broadcasts from the 10.0.0.0/30 subnet are forwarded.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
[CORRECT] The DHCP pool is misconfigured: the excluded-address range covers most of the pool (192.168.50.1 through 192.168.50.200), but leaves 192.168.50.201-254 assignable, violating the requirement. The correct configuration should exclude 192.168.50.1-9 (gateway) and 192.168.50.201-254 (upper end). The 'ip helper-address' on GigabitEthernet0/0 is unnecessary because R1 itself is the DHCP server for that subnet; it should be removed. The relay agent configuration is missing on the interface facing the remote DHCP server—'ip helper-address 203.0.113.10' should be added to GigabitEthernet0/1.
Why this is correct
The DHCP pool nearly all addresses are excluded, but the upper range .201-.254 remains available and must be explicitly excluded to meet the assignment requirement. The helper-address on G0/0 is redundant because R1 is the server for that subnet, and G0/1 lacks the required helper-address to forward requests from the 10.0.0.0/30 link.
- ✗
The DHCP pool is misconfigured: the excluded-address range should be 192.168.50.1 192.168.50.9, but the helper-address on GigabitEthernet0/0 is correct because it forwards DHCP requests to the remote server. The relay agent configuration is missing on GigabitEthernet0/1.
Why it's wrong here
This is incorrect because the helper-address on GigabitEthernet0/0 is not needed; R1 is the DHCP server for that subnet, so broadcasts should not be forwarded elsewhere. Adding a helper-address would cause DHCP requests to be forwarded to the remote server unnecessarily.
- ✗
The DHCP pool is correctly configured with excluded-address 192.168.50.1 192.168.50.9. The issue is that the 'ip helper-address' on GigabitEthernet0/1 is missing; it should be added to forward requests to the remote server. Additionally, the 'ip helper-address' on GigabitEthernet0/0 is correct because it forwards requests from VLAN 50 to the remote server.
Why it's wrong here
This is incorrect because the excluded-address range is correct, but the helper-address on GigabitEthernet0/0 is still unnecessary and should be removed. The problem statement says clients on VLAN 50 are not receiving addresses, which is due to the excluded-address covering the entire pool, not the helper-address on G0/0.
- ✗
The DHCP pool is misconfigured: the excluded-address range should be 192.168.50.1 192.168.50.9. The 'ip helper-address' on GigabitEthernet0/0 should be removed. The relay agent configuration is correct because 'ip helper-address 203.0.113.10' is already configured on GigabitEthernet0/1.
Why it's wrong here
This is incorrect because the relay agent configuration is missing; the helper-address on GigabitEthernet0/1 is not present. The option claims it is already configured, but the problem states that the relay agent configuration is missing.
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.
✓[CORRECT] The DHCP pool is misconfigured: the excluded-address range covers most of the pool (192.168.50.1 through 192.168.50.200), but leaves 192.168.50.201-254 assignable, violating the requirement. The correct configuration should exclude 192.168.50.1-9 (gateway) and 192.168.50.201-254 (upper end). The 'ip helper-address' on GigabitEthernet0/0 is unnecessary because R1 itself is the DHCP server for that subnet; it should be removed. The relay agent configuration is missing on the interface facing the remote DHCP server—'ip helper-address 203.0.113.10' should be added to GigabitEthernet0/1.Correct answer▾
Why this is correct
The DHCP pool nearly all addresses are excluded, but the upper range .201-.254 remains available and must be explicitly excluded to meet the assignment requirement. The helper-address on G0/0 is redundant because R1 is the server for that subnet, and G0/1 lacks the required helper-address to forward requests from the 10.0.0.0/30 link.
✗The DHCP pool is misconfigured: the excluded-address range should be 192.168.50.1 192.168.50.9, but the helper-address on GigabitEthernet0/0 is correct because it forwards DHCP requests to the remote server. The relay agent configuration is missing on GigabitEthernet0/1.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that a helper-address should not be configured on an interface where the router itself is the DHCP server for that subnet.
Why candidates choose this
Candidates might think that a helper-address is always needed to forward DHCP broadcasts, but they forget that the router can act as the server locally.
✗The DHCP pool is correctly configured with excluded-address 192.168.50.1 192.168.50.9. The issue is that the 'ip helper-address' on GigabitEthernet0/1 is missing; it should be added to forward requests to the remote server. Additionally, the 'ip helper-address' on GigabitEthernet0/0 is correct because it forwards requests from VLAN 50 to the remote server.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the helper-address on the LAN interface is not needed and would cause issues, and the excluded-address range is actually correct in this option, but the question's misconfiguration is the excluded-address being too broad.
Why candidates choose this
Candidates might focus only on the relay agent configuration and overlook the excluded-address misconfiguration, thinking the helper-address on G0/0 is needed for the remote server.
✗The DHCP pool is misconfigured: the excluded-address range should be 192.168.50.1 192.168.50.9. The 'ip helper-address' on GigabitEthernet0/0 should be removed. The relay agent configuration is correct because 'ip helper-address 203.0.113.10' is already configured on GigabitEthernet0/1.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the helper-address on the interface facing the remote server is not configured, so DHCP broadcasts from the 10.0.0.0/30 subnet will not be forwarded.
Why candidates choose this
Candidates might assume that the relay agent configuration is already in place because it is a common task, but they fail to verify that it is actually missing.
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?”
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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.