The correct answer is that the router is performing load balancing across two LSPs for prefix 192.168.1.0/24. This is evident because the show mpls forwarding-table output displays two distinct entries for the same prefix, each with a different outgoing interface and label action—one using Pop Label for Penultimate Hop Popping and the other forwarding with label 22—indicating that MPLS traffic is being distributed across two equal-cost paths. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to interpret MPLS forwarding-table output and recognize load balancing, a common topic in the MPLS section. A frequent trap is misreading the Pop Label entry as a sign of a single LSP, but the presence of multiple entries for the same prefix is the key indicator of load sharing. Remember the mnemonic: “Two entries, same prefix—load balancing is the fix.”
300-410 MPLS L3VPN Practice Question
This 300-410 practice question tests your understanding of mpls l3vpn. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 on Router PE1:
PE1# show mpls forwarding-table 192.168.1.0 24
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or Tunnel Id Switched interface
16 Pop Label 192.168.1.0/24 0 Gi0/0 10.1.1.2
17 22 192.168.1.0/24 0 Gi0/1 10.2.2.2
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The router is performing load balancing across two LSPs for prefix 192.168.1.0/24.
The show mpls forwarding-table output shows two entries for the same prefix. The first entry has 'Pop Label' as outgoing label, meaning PHP (Penultimate Hop Popping) is in use for that path. The second entry has label 22, indicating a different LSP. The presence of two entries for the same prefix suggests load balancing across two equal-cost paths.
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 is performing load balancing across two LSPs for prefix 192.168.1.0/24.
Why this is correct
Two forwarding entries for the same prefix with different outgoing interfaces and labels indicate ECMP load balancing.
The router has a routing loop for prefix 192.168.1.0/24.
Why it's wrong here
No evidence of loop; both paths are valid.
✗
Penultimate Hop Popping is disabled on this router.
Why it's wrong here
The first entry shows 'Pop Label', which indicates PHP is enabled.
✗
The prefix 192.168.1.0/24 is learned via BGP from two different neighbors.
Why it's wrong here
The output does not show the routing protocol; it only shows MPLS forwarding entries.
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
The first entry shows 'Pop Label', which indicates PHP is enabled.
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 L3VPN — This question tests MPLS L3VPN — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The router is performing load balancing across two LSPs for prefix 192.168.1.0/24. — The show mpls forwarding-table output shows two entries for the same prefix. The first entry has 'Pop Label' as outgoing label, meaning PHP (Penultimate Hop Popping) is in use for that path. The second entry has label 22, indicating a different LSP. The presence of two entries for the same prefix suggests load balancing across two equal-cost paths.
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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