mediumMultiple ChoiceObjective-mapped
300-410 Practice Question: Given the following configuration: ip cef !…
Given the following configuration:
ip cef
!
interface GigabitEthernet0/0 ip address 10.1.1.1 255.255.255.252
mpls ip !
interface GigabitEthernet0/1 ip address 10.2.2.1 255.255.255.252
mpls ip !
router ospf 1 network 10.0.0.0 0.255.255.255 area 0
! mpls ldp router-id Loopback0 force !
interface Loopback0 ip address 192.168.0.1 255.255.255.255
A network engineer notices that LDP sessions are not establishing. What is the most likely cause?
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 LDP router ID is not reachable because the loopback is not advertised in OSPF.
The loopback is not advertised in OSPF because the network statement 10.0.0.0 0.255.255.255 does not include 192.168.0.1. The neighbor cannot reach the LDP router ID, so LDP sessions fail. This is a common oversight.
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 OSPF network statement is too broad and causes routing issues.
Why it's wrong here
A broad network statement is fine; it advertises all interfaces within the range, but it does not include the loopback.
- ✓
The LDP router ID is not reachable because the loopback is not advertised in OSPF.
Why this is correct
The loopback 192.168.0.1 is not in the OSPF domain, so neighbors cannot route to it. LDP uses the router ID as the transport address, and without reachability, sessions cannot establish.
- ✗
The 'mpls ip' command is missing on Loopback0.
Why it's wrong here
Loopback interfaces do not need 'mpls ip' for LDP router ID; they only need to be reachable.
- ✗
The 'force' keyword prevents LDP from using any other interface if Loopback0 is down.
Why it's wrong here
The 'force' keyword does not cause failure; it simply forces the router ID. The issue is reachability.
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.
Go deeper
Related to this question
Learn chapter
Introduction to ENARSI Exam and Network Fundamentals
Key term
MPLS Label Distribution
MPLS Label Distribution is the process by which routers exchange labels that tell them how to forward packets across a network without looking at the IP address each time.
Key term
LDP Protocol
LDP, or Label Distribution Protocol, is a protocol that routers use to automatically exchange labels that enable MPLS (Multiprotocol Label Switching) to create fast, efficient paths for data packets across a network.
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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.