This 300-410 practice question tests your understanding of mpls operations. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Given the following partial configuration:
ip cef
!
interface Loopback0
ip address 10.0.0.1 255.255.255.255
!
interface GigabitEthernet0/0
ip address 10.1.1.1 255.255.255.252
mpls ip
!
router ospf 1
network 10.0.0.1 0.0.0.0 area 0
network 10.1.1.0 0.0.0.3 area 0
!
mpls ldp router-id Loopback0 force
What is missing from this configuration to ensure proper MPLS LDP operation?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Nothing is missing; the configuration is complete for basic MPLS LDP operation.
The configuration appears correct: CEF enabled, MPLS enabled on the interface, OSPF advertising all networks, and LDP router-id set to a loopback. There is no missing element for basic LDP operation. However, some might think 'mpls label protocol ldp' is needed, but it is default. The question tests if the candidate can identify that nothing is missing.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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 'mpls label protocol ldp' command is missing globally or on the interface.
Why it's wrong here
LDP is the default label distribution protocol; explicit configuration is optional.
✗
The 'mpls ldp neighbor' command is needed to specify the neighbor's IP address.
Why it's wrong here
LDP dynamically discovers neighbors via hello messages; no static neighbor configuration is required.
✓
Nothing is missing; the configuration is complete for basic MPLS LDP operation.
Why this is correct
All required components are present: CEF, interface MPLS enablement, IGP for reachability, and a stable LDP router ID.
The 'mpls ip' command must also be applied under the OSPF process.
Why it's wrong here
MPLS is enabled on interfaces, not under the routing protocol. OSPF does not require an MPLS subcommand.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Trap categories for this question
Command / output trap
MPLS is enabled on interfaces, not under the routing protocol. OSPF does not require an MPLS subcommand.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.
TExam Day Tips
→Check area mismatch first when OSPF adjacency fails.
→Review passive interfaces when a network is advertised but no neighbour forms.
→Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
MPLS Operations — This question tests MPLS Operations — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Nothing is missing; the configuration is complete for basic MPLS LDP operation. — The configuration appears correct: CEF enabled, MPLS enabled on the interface, OSPF advertising all networks, and LDP router-id set to a loopback. There is no missing element for basic LDP operation. However, some might think 'mpls label protocol ldp' is needed, but it is default. The question tests if the candidate can identify that nothing is missing.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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