200-901 Network Fundamentals Practice Question
A network engineer is troubleshooting a connectivity issue between two hosts on different subnets. The engineer suspects a problem with the default gateway configuration. Which two statements about default gateways are correct? (Choose two.)
⚠ Common exam trap
The trap here is thinking that a default gateway can be on a different subnet or that a host can automatically use multiple gateways without a redundancy protocol.
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 default gateway is used to forward packets destined for remote networks.
The default gateway must be on the same subnet as the host so that the host can reach it via ARP. It is used to forward packets destined for remote networks. Layer 3 switches can act as gateways, and multiple gateways require redundancy protocols for automatic failover. The gateway is not limited to DNS traffic.
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 default gateway is used to forward packets destined for remote networks.
Why this is correct
When a host determines that the destination IP is not on its local subnet, it forwards the packet to the default gateway. The gateway then routes the packet toward the destination. This is the primary function of a default gateway in IP networking.
- ✗
The default gateway is only used for DNS resolution.
Why it's wrong here
The default gateway is used for routing traffic to remote networks, not specifically for DNS. DNS queries may be sent to a DNS server, which could be on a remote network, and thus would use the default gateway. However, the gateway's role is general packet forwarding, not limited to DNS.
- ✓
The default gateway must be on the same subnet as the host.
Why this is correct
For a host to communicate with devices on other subnets, it must be able to reach the default gateway at Layer 2. Therefore, the gateway's IP address must be within the same subnet as the host's IP address. If it is not, the host cannot ARP for the gateway's MAC address and will not forward packets.
- ✗
A host can have multiple default gateways configured for redundancy without any additional protocols.
Why it's wrong here
While a host can have multiple default gateways in its configuration (e.g., via DHCP options), standard IP hosts do not automatically fail over between them without a first-hop redundancy protocol like VRRP or HSRP. Typically, only one default gateway is active; additional gateways may be used if the primary fails, but this requires manual or protocol-based failover.
- ✗
The default gateway must be a router; a Layer 3 switch cannot serve as a default gateway.
Why it's wrong here
A Layer 3 switch can function as a default gateway if it has an IP interface configured on the host's subnet and routing enabled. Many enterprise networks use Layer 3 switches for inter-VLAN routing and as gateways. The statement is false because it incorrectly excludes Layer 3 switches.
Visual reference
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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