mediumMultiple Choice
Interpreting show mpls ldp bindings Output
A network engineer runs the following command on Router R3:
R3# show mpls ldp bindings
lib entry: 10.1.1.1/32, rev 2 local binding: label: 16 remote binding: lsr: 10.1.1.2:0, label: 17 lib entry: 10.2.2.0/24, rev 4 local binding: label: 18 remote binding: lsr: 10.1.1.2:0, label: 19 lib entry: 10.3.3.0/24, rev 6 local binding: label: 20 remote binding: lsr: 10.1.1.2:0, label: 21
Based on this output, what is true?
Quick Answer
The correct interpretation is that for prefix 10.1.1.1/32, the local label is 16 and the remote label from LSR 10.1.1.2 is 17. This is because the show mpls ldp bindings command displays the Label Information Base (LIB), which lists every prefix learned via LDP along with two key bindings: the local label that this router (R3) has assigned, and the remote label advertised by a neighboring Label Switch Router (LSR). In the output, each "lib entry" shows a prefix, followed by its local binding and then the remote binding from a specific LSR—here, 10.1.1.2. On the ENCOR 350-401 exam, this command tests your ability to read the LIB and distinguish between locally assigned labels and labels learned from peers, a common point of confusion. A frequent trap is mixing up the local and remote labels, or assuming the "rev" number indicates label priority when it is simply a revision counter. Memory tip: think of "local" as what your router gives out, and "remote" as what your neighbor sends you—like a handshake where each side offers its own label.
⚠ Common exam trap
Cisco often tests the ability to correctly interpret 'show mpls ldp bindings' output, specifically the trap is that candidates confuse the remote label as the label the local router will use to forward traffic, when in fact the remote label is what the peer uses to reach the FEC.
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
✓
For prefix 10.1.1.1/32, the local label is 16 and the remote label from LSR 10.1.1.2 is 17.
The output of 'show mpls ldp bindings' directly shows that for prefix 10.1.1.1/32, the local label assigned by R3 is 16, and the remote label learned from LSR 10.1.1.2 (its LDP peer) is 17. This is a straightforward reading of the command output, confirming the local and remote label bindings for that FEC.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
For prefix 10.1.1.1/32, the local label is 16 and the remote label from LSR 10.1.1.2 is 17.
Why this is correct
The output directly shows, for prefix 10.1.1.1/32, a local binding of label 16 and a remote binding advertised by LSR 10.1.1.2:0 with label 17. This satisfies the stem's requirement to interpret the LDP bindings table, confirming both label values and the advertising peer exactly as displayed.
- ✗
The router has learned label bindings from two different LDP peers.
Why it's wrong here
Every remote binding in the output lists the same LSR identifier, 10.1.1.2:0, so only one LDP peer has advertised labels. It is tempting because multiple remote bindings appear, and this would be true if the remote binding lines showed differing LSR IDs.
- ✗
The label for prefix 10.2.2.0/24 is 18 locally and 19 remotely, indicating that the remote LSR will use label 18.
Why it's wrong here
The remote LSR advertises label 19 for 10.2.2.0/24 and will impose that value on traffic it forwards; label 18 is R3's local binding. It is tempting because both numbers appear on the same entry, and swapping them would be correct if the roles of local and remote were reversed.
- ✗
The LIB entry for 10.3.3.0/24 has a revision number of 6, meaning it was the sixth entry added.
Why it's wrong here
The revision number is an internal LIB version counter that increments on binding changes, not a sequential count of added entries. It is tempting because 'rev 6' looks like an ordinal, and this would hold if the field tracked insertion order rather than modification history.
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Same concept, more angles
1 more way this is tested on 350-401
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network engineer runs the following command on Router R9: R9# show mpls ldp bindings 10.9.9.0 255.255.255.0 lib entry: 10.9.9.0/24, rev 10 local binding: label: 22 remote binding: lsr: 10.9.9.1:0, label: 23 remote binding: lsr: 10.9.9.2:0, label: 24 remote binding: lsr: 10.9.9.3:0, label: 25 Based on this output, how many remote LDP peers have advertised a label for the prefix 10.9.9.0/24?
easy- A.1
- B.2
- ✓ C.3
- D.4
Why C: The output shows three remote bindings, each from a different LSR (10.9.9.1:0, 10.9.9.2:0, and 10.9.9.3:0), advertising a label for the prefix 10.9.9.0/24. The local binding (label 22) is not a remote peer, so only the three remote entries count. Therefore, the correct answer is 3.
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.