CCNA Network Services and Security Practice Question
A host has a valid IP address and subnet mask from DHCP but cannot reach remote networks because no gateway was provided. What is the best explanation?
⚠ Common exam trap
A common exam trap is assuming that a host without a default gateway cannot communicate at all. Many candidates mistakenly believe that missing a gateway disables all network communication, but in reality, the host can still communicate with devices on its local subnet using ARP. The trap lies in confusing local subnet communication with remote network access. The question specifically tests understanding that the lack of a gateway prevents forwarding to remote networks, not local connectivity. Misreading this can lead to selecting incorrect options that focus on ARP or subnet expansion rather than the gateway role.
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
✓
The host has no next-hop gateway for traffic destined outside its local subnet.
The best explanation is that the host has no next-hop path for off-subnet traffic. In plain language, the device knows what its own local network looks like, but it does not know where to send packets when the destination is outside that local range. Without a default gateway, remote communication usually fails even though local communication can still work. This is a core host-configuration concept. The correct answer is the one focused on the absence of a next hop for remote destinations.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The host has no next-hop gateway for traffic destined outside its local subnet.
Why this is correct
A DHCP lease supplies the host's IP address, subnet mask, and often a default gateway, but without that gateway entry the host's routing table contains no route for off-subnet destinations. When a packet's destination IP is outside the host's local subnet, the host must send it to a next-hop router; in its absence, the packet is dropped or never transmitted. The host can still communicate with neighbors on the same subnet, but it is effectively isolated from all other networks.
- ✗
The host cannot use ARP on the local network anymore.
Why it's wrong here
This is incorrect because ARP is a Layer 2 process used to map IP addresses to MAC addresses for hosts on the same broadcast domain. A missing default gateway has no effect on the host's ability to send ARP requests or process ARP replies, as ARP does not involve routing decisions. The host can continue to resolve and reach local neighbors via ARP even when it lacks a gateway for off-subnet traffic.
When this WOULD be correct
In a different scenario where a question states that a host is unable to communicate with any devices on the local network and has been misconfigured with an incorrect subnet mask, option B could be correct, as ARP requests would fail due to the host being unable to identify devices in the same subnet.
- ✗
The host automatically becomes part of every remote subnet.
Why it's wrong here
This statement is false because subnet membership is determined exclusively by the host's IP address and subnet mask, not by the presence or absence of a default gateway. A host with a DHCP-assigned address and mask remains a member of only its own local subnet, regardless of whether a gateway is configured. Remote subnets are reachable only through routers; the host does not automatically join or become part of them simply because DHCP succeeded.
When this WOULD be correct
In a question where a host is configured with multiple subnets and routing protocols are enabled, stating that it automatically becomes part of every remote subnet could be correct if discussing a scenario involving dynamic routing or a specific network design that allows for such behavior.
- ✗
The host must convert its access port into a trunk.
Why it's wrong here
This is wrong because switchport trunking is a Layer 2 feature used to carry multiple VLANs between switches or between a switch and a router, typically with 802.1Q tagging. A missing default gateway is a Layer 3 IP configuration issue on the host, and changing the switchport to trunk mode would not provide the host with a next-hop address or enable routing. The access port remains appropriate for carrying untagged traffic from the host, and the problem lies solely in the host's routing table, not in the switchport mode.
When this WOULD be correct
In a scenario where a question asks about VLAN configurations and the need for a switch port to carry multiple VLANs for inter-VLAN routing, converting an access port to a trunk would be the correct answer. This would apply if the question specified that the host needs to communicate across different VLANs.
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.
✓The host has no next-hop gateway for traffic destined outside its local subnet.Correct answer▾
Why this is correct
A DHCP lease supplies the host's IP address, subnet mask, and often a default gateway, but without that gateway entry the host's routing table contains no route for off-subnet destinations. When a packet's destination IP is outside the host's local subnet, the host must send it to a next-hop router; in its absence, the packet is dropped or never transmitted. The host can still communicate with neighbors on the same subnet, but it is effectively isolated from all other networks.
✗The host cannot use ARP on the local network anymore.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because the host can still use ARP to resolve IP addresses to MAC addresses within its local subnet, even without a gateway. The absence of a gateway only affects the host's ability to reach networks outside its own subnet.
★ When this WOULD be the correct answer
In a different scenario where a question states that a host is unable to communicate with any devices on the local network and has been misconfigured with an incorrect subnet mask, option B could be correct, as ARP requests would fail due to the host being unable to identify devices in the same subnet.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of ARP functionality, thinking that a lack of a gateway affects local network communication, leading to confusion about the role of ARP in local subnet communication.
✗The host automatically becomes part of every remote subnet.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because a host cannot automatically become part of every remote subnet; it can only communicate with devices on its own subnet unless a gateway is provided for routing.
★ When this WOULD be the correct answer
In a question where a host is configured with multiple subnets and routing protocols are enabled, stating that it automatically becomes part of every remote subnet could be correct if discussing a scenario involving dynamic routing or a specific network design that allows for such behavior.
Why candidates choose this
Candidates may find this option tempting due to a misunderstanding of how subnets and routing work, mistakenly believing that a device can communicate across all networks without proper routing configurations.
✗The host must convert its access port into a trunk.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because converting an access port into a trunk does not address the issue of routing traffic to remote networks; it pertains to VLAN configurations rather than gateway settings.
★ When this WOULD be the correct answer
In a scenario where a question asks about VLAN configurations and the need for a switch port to carry multiple VLANs for inter-VLAN routing, converting an access port to a trunk would be the correct answer. This would apply if the question specified that the host needs to communicate across different VLANs.
Why candidates choose this
Candidates might choose this option due to confusion between layer 2 switching and layer 3 routing concepts, mistakenly believing that port configuration changes can resolve routing issues.
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
Quick reference
IPv4 Address Class Summary
| Class | First Octet Range | Default Mask | Networks | Hosts per Network |
|---|---|---|---|---|
| A | 1–126 | /8 (255.0.0.0) | 126 | 16,777,214 |
| B | 128–191 | /16 (255.255.0.0) | 16,384 | 65,534 |
| C | 192–223 | /24 (255.255.255.0) | 2,097,152 | 254 |
| D | 224–239 | N/A | Multicast groups | — |
| E | 240–255 | N/A | Reserved / experimental | — |
127.x.x.x is reserved for loopback. Modern networks use CIDR (classless) rather than classful addressing.
Go deeper
Related to this question
Learn chapter
Device File Management with SFTP and SCP
Key term
DHCP
Dynamic Host Configuration Protocol (DHCP) automatically assigns IP addresses and network settings to devices on a network, so they can communicate without manual configuration.
Key term
Subnet mask
A subnet mask is a 32-bit number that helps a computer or network device determine which part of an IP address identifies the network and which part identifies the host device on that network.
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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.