Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
Which statement best describes the relationship between a default gateway and a host’s subnet mask in IPv4?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
The subnet mask determines whether a destination is local, and the default gateway is used for remote destinations.
This is correct because the host uses both pieces together when deciding how to send traffic.
B
Distractor review
The default gateway replaces the need for the subnet mask.
This is wrong because the host still needs the mask to determine local versus remote scope.
C
Distractor review
The subnet mask is used only by routers, not by hosts.
This is wrong because hosts use the subnet mask directly.
D
Distractor review
The default gateway is used only for broadcast traffic.
This is wrong because the gateway is used for off-subnet forwarding, not just broadcast.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is assuming that the default gateway replaces the subnet mask or that it is involved in all traffic forwarding decisions. Candidates might think the gateway handles broadcast traffic or that the subnet mask is irrelevant once a gateway is set. This misunderstanding leads to incorrect conclusions about how hosts decide where to send packets. The subnet mask is essential for the host to determine if a destination is local or remote, while the default gateway is only used when the destination is outside the local subnet. Confusing these roles can cause errors in network design and troubleshooting scenarios.
Technical deep dive
How to think about this question
In IPv4 networking, the subnet mask is a critical component that defines the network and host portions of an IP address. It allows a host to determine whether a destination IP address resides within the same local subnet or on a remote network. This distinction is essential because it dictates how the host forwards packets—either directly within the local network or via a router. The subnet mask works by masking the IP address bits to isolate the network prefix, enabling the host to compare its own network portion with the destination's network portion. When a host needs to send a packet, it first applies its subnet mask to both its own IP address and the destination IP address. If the resulting network addresses match, the destination is local, and the host uses Address Resolution Protocol (ARP) to find the destination MAC address and send the packet directly. If the network addresses differ, the destination is remote, and the host forwards the packet to its configured default gateway. The default gateway is typically a router interface that knows how to route packets beyond the local subnet. A common exam trap is misunderstanding the roles of the subnet mask and default gateway. Some candidates mistakenly believe the default gateway replaces the need for a subnet mask or that the gateway handles broadcast traffic exclusively. In reality, the subnet mask is indispensable for determining local versus remote destinations, and the default gateway is only used for off-subnet traffic forwarding. Misinterpreting these roles can lead to incorrect routing decisions and packet delivery failures in practical networks.
KKey Concepts to Remember
- A host uses its subnet mask to determine if a destination IP address is within the same local subnet or a remote network.
- The subnet mask enables the host to compare its network portion of the IP address with the destination’s network portion.
- If the destination is local, the host sends packets directly using ARP to resolve the destination MAC address.
- If the destination is remote, the host forwards packets to the default gateway for routing beyond the local subnet.
- The default gateway is a router interface that provides the next hop for off-subnet traffic from the host.
- The subnet mask and default gateway work together to ensure correct packet forwarding decisions on IPv4 networks.
- The default gateway does not replace the subnet mask and is not involved in local subnet traffic delivery.
- Broadcast traffic is handled differently and is not forwarded by the default gateway.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
A host uses its subnet mask to determine if a destination IP address is within the same local subnet or a remote network.
What is the correct answer to this question?
The correct answer is: The subnet mask determines whether a destination is local, and the default gateway is used for remote destinations. — The subnet mask helps the host decide whether a destination is local or remote, and the default gateway is used when the destination is remote. In practical terms, the mask tells the host whether it should ARP locally or send the packet toward the router. The gateway then provides the next hop for off-subnet traffic. This is one of the most foundational host-networking relationships in IPv4.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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