CCNA Network Services and Security Practice Question
A branch router is acting as a DHCP server. Which two parameters can it provide directly to clients through DHCP?
⚠ Common exam trap
Cisco often tests the distinction between DHCP-provided parameters (Layer 3/4) and switch-specific or routing protocol parameters (Layer 2/3), leading candidates to mistakenly select options like OSPF area or STP priority that are not DHCP options.
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
✓
Default gateway
DHCP (Dynamic Host Configuration Protocol) is designed to automatically assign IP configuration parameters to clients. The default gateway (option 3) and DNS server address (option 6) are standard DHCP options defined in RFC 2132, which a router acting as a DHCP server can directly provide to clients to enable network connectivity and name resolution.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Default gateway
Why this is correct
DHCP Option 3 (Router) is used by clients to reach subnets beyond their local segment. When a branch router acts as a DHCP server, it must advertise a default gateway—typically its own LAN interface address—so endpoints can send off-subnet traffic. Without this parameter, clients can only communicate within the local broadcast domain.
- ✓
DNS server address
Why this is correct
DHCP Option 6 (Domain Name Server) delivers the IP address of DNS resolvers to clients, enabling them to resolve hostnames to addresses. A branch router acting as DHCP server commonly points clients to either its own DNS forwarding service or an upstream provider's resolver. This is a standard client lease parameter because name resolution is required for normal Internet use.
- ✗
OSPF area number
Why it's wrong here
OSPF area numbers are routing protocol construct that partition an autonomous system for link-state advertisement scoping; they are not DHCP options because DHCP distributes host TCP/IP settings, not routing daemon parameters. The router's OSPF process uses area numbers on its own interfaces to build the routing table, but clients never need this value, as they do not run OSPF. Sending such a value via DHCP would be meaningless and protocol-incompatible.
When this WOULD be correct
In a question about OSPF configuration on a router, where you need to specify the area number for an interface under the OSPF process, e.g., 'network 192.168.1.0 0.0.0.255 area 0'.
- ✗
Switch port duplex setting
Why it's wrong here
Switch port duplex settings define physical-layer negotiation behavior (half/full duplex) on an Ethernet port, which is configured locally on the switch interface via CLI or autonegotiation. DHCP operates at L3/L4 and carries customer premise configuration like IP address and lease duration; it never instantiates L1 physical interface parameters. A client receiving a DHCP lease would have no mechanism to apply a duplex value to its NIC or to the switch port it is attached to.
When this WOULD be correct
In a question about switch port configuration, such as 'Which parameter is configured on a switch interface to match the connected device's capabilities?', switch port duplex setting would be correct.
- ✗
STP root bridge priority
Why it's wrong here
STP root bridge priority is a bridge parameter used in spanning-tree elections on L2 switches to determine which switch becomes the root; it's a control-plane setting applied to the switch itself. DHCP, on the other hand, operates at the application layer to lease L3 addressing and endpoint configuration details. Even if the router also runs STP on its switchports, the root priority is not something a DHCP client could receive or use.
When this WOULD be correct
In a question asking 'Which parameter is used in STP to determine the root bridge?', STP root bridge priority would be the correct answer, as it influences the root bridge election process.
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.
✓Default gatewayCorrect answer▾
Why this is correct
DHCP Option 3 (Router) is used by clients to reach subnets beyond their local segment. When a branch router acts as a DHCP server, it must advertise a default gateway—typically its own LAN interface address—so endpoints can send off-subnet traffic. Without this parameter, clients can only communicate within the local broadcast domain.
✗OSPF area numberWrong answer — click to see why▾
Why this is wrong here
DHCP provides IP configuration parameters like default gateway and DNS server, not routing protocol parameters. OSPF area number is a routing protocol setting configured manually on routers, not assigned via DHCP.
★ When this WOULD be the correct answer
In a question about OSPF configuration on a router, where you need to specify the area number for an interface under the OSPF process, e.g., 'network 192.168.1.0 0.0.0.255 area 0'.
Why candidates choose this
Candidates may confuse DHCP options with network configuration parameters, thinking DHCP can assign any network-related setting, including routing protocol details.
✗Switch port duplex settingWrong answer — click to see why▾
Why this is wrong here
DHCP provides IP configuration parameters like default gateway and DNS server, not physical layer settings like switch port duplex. Duplex is configured locally on the switch interface, not assigned via DHCP.
★ When this WOULD be the correct answer
In a question about switch port configuration, such as 'Which parameter is configured on a switch interface to match the connected device's capabilities?', switch port duplex setting would be correct.
Why candidates choose this
Candidates may confuse DHCP's ability to provide network-layer parameters with physical-layer settings, or think DHCP can configure any device setting remotely.
✗STP root bridge priorityWrong answer — click to see why▾
Why this is wrong here
STP root bridge priority is a Spanning Tree Protocol parameter used to elect the root bridge in a switched network, not a DHCP-provided parameter. DHCP can only supply IP configuration parameters like default gateway and DNS server.
★ When this WOULD be the correct answer
In a question asking 'Which parameter is used in STP to determine the root bridge?', STP root bridge priority would be the correct answer, as it influences the root bridge election process.
Why candidates choose this
Candidates may confuse DHCP with other network services or protocols, mistakenly thinking DHCP can provide Layer 2 or routing protocol parameters, especially when studying multiple topics simultaneously.
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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Related to this question
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Key term
Name Server
A name server is a specialized server that translates human-readable domain names into machine-readable IP addresses so that computers can find each other on a network.
Key term
DNS
DNS is the system that translates human-friendly domain names like example.com into machine-readable IP addresses so computers can find each other on a network.
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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.