mediumMultiple Choice
300-410 Practice Question: Given the following partial configuration on…
Given the following partial configuration on router R5:
interface GigabitEthernet0/0 ip address 10.1.1.1 255.255.255.0 ip pim sparse-mode
!
interface GigabitEthernet0/1 ip address 10.2.2.1 255.255.255.0 ip pim sparse-mode
!
router ospf 1
router-id 5.5.5.5
network 10.0.0.0 0.255.255.255 area 0
What is the effect of this configuration?
⚠ Common exam trap
Cisco often tests the misconception that enabling PIM sparse-mode on an interface disrupts OSPF adjacency formation, when in fact they operate at different layers (OSPF at Layer 3 routing, PIM at multicast routing) and do not interfere with each other.
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
✓
OSPF will form adjacencies on both interfaces, and PIM sparse-mode will operate normally; the configuration is valid.
The configuration is valid because OSPF and PIM sparse-mode operate independently on an interface. OSPF uses multicast address 224.0.0.5/6 for hello packets and forms adjacencies regardless of PIM sparse-mode being enabled. PIM sparse-mode requires an RP to function, but its presence does not affect OSPF adjacency formation. The network statement 10.0.0.0 0.255.255.255 matches both interfaces (10.1.1.1 and 10.2.2.1), so OSPF will form adjacencies on both.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
OSPF will not form adjacencies because PIM sparse-mode is enabled on the interfaces.
Why it's wrong here
PIM sparse-mode is independent of OSPF; enabling it on an interface does not block OSPF hello processing or adjacency formation. It would be relevant if the question concerned multicast rendezvous point or RPF behaviour, not unicast routing adjacency.
- ✓
OSPF will form adjacencies on both interfaces, and PIM sparse-mode will operate normally; the configuration is valid.
Why this is correct
PIM sparse-mode requires a unicast routing table entry to build its RPF neighbour, and OSPF supplies that by advertising both 10.1.1.0/24 and 10.2.2.0/24 into area 0 via the single classful network statement. With router-id 5.5.5.5 set, adjacencies form and multicast forwarding operates normally.
- ✗
OSPF will only form adjacency on GigabitEthernet0/0 because the network statement does not match GigabitEthernet0/1.
Why it's wrong here
The network statement uses the 0.255.255.255 wildcard mask, which matches both 10.1.1.0/24 and 10.2.2.0/24, so OSPF enables on both interfaces and adjacencies can form on each. It is tempting because a /24 network statement would indeed match only one interface, but here the wildcard is deliberately broad.
- ✗
PIM sparse-mode will not work because there is no rendezvous point (RP) configured.
Why it's wrong here
PIM sparse-mode can operate without a statically configured RP if dynamic RP discovery (e.g., Auto-RP or BSR) is used, or if the RP is learned via other means. The absence of an RP does not prevent PIM from operating, but multicast forwarding may be limited.
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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JA
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.