mediumMultiple Choice
300-410 Practice Question: Given the following partial configuration on…
Given the following partial configuration on router R1:
router eigrp 100 network 10.0.0.0 0.255.255.255 network 192.168.1.0 0.0.0.255
!
interface GigabitEthernet0/0 ip address 10.1.1.1 255.255.255.0
!
interface GigabitEthernet0/1 ip address 192.168.1.1 255.255.255.0
!
interface GigabitEthernet0/2 ip address 172.16.1.1 255.255.255.0
What is the effect of this configuration?
⚠ Common exam trap
Cisco often tests the misconception that a network statement with a wildcard mask will automatically include all interfaces with similar first octets, but in reality, the wildcard mask must explicitly match the exact subnet range for an interface to be enabled.
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
✓
EIGRP will only advertise the 10.1.1.0/24 and 192.168.1.0/24 networks; the 172.16.1.0/24 network will not be advertised and no EIGRP adjacency will be formed on that interface.
EIGRP uses the network command with a wildcard mask to determine which interfaces to enable EIGRP on. The network 10.0.0.0 0.255.255.255 matches interfaces with an IP address in the 10.x.x.x range, enabling EIGRP on GigabitEthernet0/0 (10.1.1.1). The network 192.168.1.0 0.0.0.255 matches the 192.168.1.0/24 subnet, enabling EIGRP on GigabitEthernet0/1 (192.168.1.1). The 172.16.1.0/24 network is not matched by any network statement, so EIGRP is not enabled on GigabitEthernet0/2, and no adjacency is formed there.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
EIGRP will form adjacencies and advertise all three interfaces because the network statements use classful boundaries.
Why it's wrong here
EIGRP network statements without an explicit wildcard mask default to the classful boundary of the major network, but this only applies to the networks explicitly configured. The statements for 10.0.0.0 and 192.168.1.0 cover those respective major networks, not the entirely separate 172.16.0.0 major network. Since the 172.16.1.0/24 interface belongs to an unconfigured major network, that interface will not have EIGRP enabled, so the claim that all three interfaces will be advertised is false.
- ✓
EIGRP will only advertise the 10.1.1.0/24 and 192.168.1.0/24 networks; the 172.16.1.0/24 network will not be advertised and no EIGRP adjacency will be formed on that interface.
Why this is correct
EIGRP only enables the protocol on interfaces whose IP address falls within a network explicitly listed by a network statement. Here, 10.1.1.0/24 matches the 10.0.0.0/8 network statement, and 192.168.1.0/24 directly matches the 192.168.1.0 statement. However, 172.16.1.0/24 is part of the 172.16.0.0/16 major network, which is never referenced by any network statement, so EIGRP will not run on that interface and no adjacency will form there.
- ✗
EIGRP will advertise all three networks because the network 10.0.0.0 command includes all interfaces with an IP starting with 1, 172, or 192.
Why it's wrong here
The misconception in this option is treating the 10.0.0.0 network statement as if it captured any IP address with a leading octet of 1, 172, or 192. In EIGRP, the network 10.0.0.0 command matches only addresses within the 10.0.0.0/8 range, because 10.0.0.0 is a Class A network. The interfaces with IPs 172.16.1.1 and 192.168.1.1 belong to different major networks and are not subsumed by 10.0.0.0, so this statement alone does not advertise all three networks.
- ✗
EIGRP will not form any adjacencies because the network statements must use exact subnet masks instead of wildcard masks.
Why it's wrong here
The configuration does not require subnet masks in the EIGRP network statements; EIGRP accepts classful network numbers or classful network plus an optional wildcard mask. The given statements are syntactically valid and will enable EIGRP on the interfaces they match. The actual issue is that neither statement covers the 172.16.1.0/24 subnet, while the 10.1.1.0/24 and 192.168.1.0/24 interfaces are correctly matched, so adjacencies will form on those two but not on the 172.16.1.0/24 interface.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 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 300-410 exam.