The answer is that the router has an operational LDP session with neighbor 10.0.0.2, with addresses 10.0.0.2, 10.1.1.2, and 10.2.2.2. This is correct because the "State: Oper" field confirms the session is fully established and exchanging label information, while the "TCP connection: 10.0.0.2.646 - 10.0.0.1.646" shows the reliable transport using well-known port 646 between the two LDP peers. On the Cisco CCNP ENARSI 300-410 exam, interpreting MPLS LDP neighbor details like this tests your ability to verify label distribution protocol health, often in troubleshooting scenarios where a missing or "Oper" state can indicate a routing or firewall issue blocking TCP 646. A common trap is confusing the "Downstream" label advertisement mode with the session state—remember that "Downstream" is the default unsolicited mode, not a failure indicator. For a quick memory tip, think "TCP 646, State Oper, addresses bound" to recall the three key checks when reviewing LDP neighbor details.
300-410 Network Logging and Syslog Practice Question
This 300-410 practice question tests your understanding of network logging and syslog. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A network engineer runs the following command to troubleshoot a Network Logging and Syslog issue:
R1# show mpls ldp neighbor detail
Output:
Peer LDP Ident: 10.0.0.2:0, Local LDP Ident: 10.0.0.1:0
TCP connection: 10.0.0.2.646 - 10.0.0.1.646
State: Oper; Msgs sent/rcvd: 100/100; Downstream
Up time: 00:10:00
LDP discovery sources:
GigabitEthernet0/0, Src IP addr: 10.0.0.2
Addresses bound to peer LDP Ident:
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The router has an operational LDP session with neighbor 10.0.0.2, with addresses 10.0.0.2, 10.1.1.2, and 10.2.2.2.
The output shows detailed LDP neighbor information, including TCP connection details, state, and addresses bound to the peer. This indicates a functioning LDP session.
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 router has an operational LDP session with neighbor 10.0.0.2, with addresses 10.0.0.2, 10.1.1.2, and 10.2.2.2.
Why this is correct
The state is 'Oper' (operational) and addresses are listed.
The router is experiencing an LDP authentication failure.
Why it's wrong here
No authentication errors are shown.
✗
The router is using UDP for LDP discovery.
Why it's wrong here
LDP discovery uses UDP, but the session uses TCP; the output shows TCP connection.
✗
The router has only one LDP neighbor.
Why it's wrong here
The output shows only one neighbor, but does not indicate if there are others.
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
No authentication errors are shown.
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.
Network Logging and Syslog — This question tests Network Logging and Syslog — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The router has an operational LDP session with neighbor 10.0.0.2, with addresses 10.0.0.2, 10.1.1.2, and 10.2.2.2. — The output shows detailed LDP neighbor information, including TCP connection details, state, and addresses bound to the peer. This indicates a functioning LDP session.
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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