20+ practice questions focused on Subnetting — one of the most tested topics on the CCNA 200-301 v2 exam. Each question includes a detailed explanation so you learn why the right answer is correct.
Start Subnetting PracticeA network engineer notices that internal hosts (192.168.1.0/24) can reach external servers on the internet, but replies from external servers never reach the internal hosts. The router R1 is configured with dynamic NAT to translate the internal subnet to a pool of public IPs (203.0.113.10-203.0.113.20). The engineer runs 'show ip nat translations' and sees only a few stale translations. What is the most likely cause of the issue?
Explanation: The 'ip nat outside' command must be applied to the interface facing the external network (GigabitEthernet0/0) for the router to translate return traffic. Without it, the router does not perform NAT on packets arriving on that interface, so replies from external servers are forwarded without translation back to the inside local IPs, which are not routable on the internet. The stale translations indicate that outbound translations were created but never used for return traffic, confirming the missing outside interface command.
A network administrator is troubleshooting an IPv6 connectivity issue on a newly deployed router. The router's G0/0/0 interface is configured with an IPv6 address using EUI-64, but hosts on that subnet cannot reach the router's link-local address. The administrator runs 'show ipv6 interface g0/0/0' and sees that the interface is up/up but the IPv6 address is not in the expected format. What is the most likely cause of the problem?
Explanation: The router's G0/0/0 interface is up/up, but the IPv6 address is not in the expected EUI-64 format. This indicates that the 'ipv6 address' command was likely omitted entirely, because if it were simply misconfigured (e.g., without the `eui-64` keyword), the router would still automatically generate a link-local address, and hosts would be able to reach it. Since hosts cannot reach the link-local address, IPv6 is not enabled on the interface at all. The correct configuration requires the `ipv6 address` command with the appropriate prefix and the `eui-64` keyword.
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?
Explanation: 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.
Based on the exhibit, which action is most likely required to allow AP-22 to join the controller successfully?
Explanation: The correct action is to fix the AP's default gateway so it can reach the controller's subnet. Option B is wrong because APs use Ethernet, not PPP encapsulation, which is used for serial WAN links. Option C is wrong because CAPWAP does not assign IP addresses; DHCP does, but the AP already has a static IP, and removing it would cause it to fall back to DHCP, which may not fix the gateway issue. Option D is wrong because disabling DHCP on the controller would affect all APs and prevent new APs from obtaining addresses, which is not a targeted fix.
A wireless client joins the correct SSID and gets an address in the correct employee subnet, but cannot reach only one internal application while everything else works. Which troubleshooting area is the strongest first target?
Explanation: The strongest first target is the application path or policy specific to that application because the client already has general connectivity: it joined the correct SSID, authenticated, and obtained an IP address in the employee subnet. A failure limited to one internal application indicates that basic WLAN join, DHCP, and overall routing are working; therefore, ACLs, firewall rules, DNS resolution for that service, or application-specific policies are the likely cause. Option B (SSID broadcast setting) is irrelevant because the client successfully joined the SSID and has connectivity. Option C (voice VLAN on the wired access port) is not a first target because the symptom involves a single data application, not voice, and the client is on the employee subnet, not a voice VLAN. Option D (OSPF router ID on the client) is invalid because client devices do not typically run OSPF; OSPF runs on routers, not wireless clients.
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Practice all Subnetting questions1. Baseline your knowledge
Start with 10 questions to gauge your current understanding of Subnetting. This tells you whether you need a concept refresher or just practice.
2. Review every explanation
For each question — right or wrong — read the full explanation. Understanding why an answer is correct is more valuable than knowing the answer itself.
3. Focus on exam traps
Subnetting questions on the 200-301 frequently use trap wording. Look for subtle differences in answers that test your precision, not just general knowledge.
4. Reach 80% consistently
Do repeated sessions until you score 80%+ three times in a row. Then move to mixed-mode practice to test cross-topic recall under realistic conditions.
The exact number varies per candidate. Subnetting is tested as part of the CCNA 200-301 v2 blueprint. Practicing with targeted Subnetting questions ensures you can handle any format or difficulty that appears.
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Difficulty is subjective, but Subnetting is a high-priority exam concept tested in multiple ways — direct recall, scenario analysis, and command-output interpretation. Consistent practice is the best way to build confidence.
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