mediumMultiple Choice
350-401 Practice Question: Runs the following command on Router R4: R4# show…
A network engineer runs the following command on Router R4:
R4# show mpls ldp neighbor
Peer LDP Ident: 10.0.0.2:0; Local LDP Ident 10.0.0.1:0 TCP connection: 10.0.0.2.646 - 10.0.0.1.54567 State: Oper; Msgs sent/rcvd: 100/95; Downstream Up time: 00:15:30 LDP discovery sources: GigabitEthernet0/0, Src IP addr: 10.0.0.2 Addresses bound to peer LDP Ident:
10.0.0.2 192.168.1.1
Based on this output, what can be concluded?
⚠ Common exam trap
Cisco often tests the distinction between LDP neighbor discovery (via UDP hellos) and LDP session establishment (via TCP), and candidates may confuse the 'Addresses bound' field with label bindings, leading them to incorrectly select option D.
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 session is established over the GigabitEthernet0/0 interface.
The output shows 'State: Oper' (Operational), which indicates the LDP session is fully established and operational. The 'LDP discovery sources' line lists GigabitEthernet0/0 as the interface through which the peer (10.0.0.2) was discovered, confirming that the LDP session is established over that interface. This is the correct interpretation of the show command.
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 LDP session is down due to a TCP connection issue.
Why it's wrong here
The neighbor output shows the state as 'Oper', which is the operational state for an established LDP session. An LDP session that is down due to a TCP connection issue would appear as 'Nonoper' or not be listed at all, because the TCP transport must be successfully established before the session can become operational. Therefore, the statement that the session is down because of a TCP issue directly contradicts the operational state shown in the command output, making this answer incorrect.
- ✓
The LDP session is established over the GigabitEthernet0/0 interface.
Why this is correct
In the output of 'show mpls ldp neighbor', the 'Discovery Source' (or 'Discovery sources') field lists the interface through which LDP hello messages were received from the peer. Since the output shows GigabitEthernet0/0 as the discovery source, the neighbor adjacency was formed over that interface, and the LDP session (which uses a TCP connection for label exchange) is consequently established over that interface. This confirms that LDP is operating correctly on GigabitEthernet0/0, which is why this answer is correct.
- ✗
The peer is not sending any LDP messages.
Why it's wrong here
The neighbor output includes counters such as 'Messages sent/rcvd' showing 100 sent and 95 received. This indicates that the peer is actively transmitting LDP messages, because the received counter increments only when LDP packets (like Hello, Keepalive, or Label Mapping) arrive from that peer. If the peer were not sending any messages, the received count would remain at zero or not increase, and the session would likely not remain operational in the 'Oper' state, so this answer is wrong.
- ✗
The local router has only one label binding for the peer.
Why it's wrong here
The 'Address Bound' or 'Address' information shown in 'show mpls ldp neighbor' detail is a list of the peer's IP addresses that were advertised to the local router via LDP Address messages, not a list of label bindings. Label bindings, which map FECs to labels, are only visible using 'show mpls ldp bindings'. Therefore, the neighbor output cannot be used to conclude that the local router has only one label binding for the peer; that would require a separate command, making the statement incorrect.
Visual reference
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 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 350-401 exam.