350-501 MPLS and Segment Routing Practice Question
Exhibit
Refer to the exhibit.
PE1# show mpls forwarding-table
Local Outgoing Prefix Labels Label Next Hop
16 Pop 10.1.1.0/24
No Label 10.2.2.0/24
PE1# show ip bgp vpnv4 vrf CUSTOMER
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 100:1
10.1.1.0/24 192.168.1.1 0 100 0 65001 i
10.2.2.0/24 192.168.2.2 0 100 0 65002 iRefer to the exhibit. A PE router in an MPLS L3VPN network shows the above output. The VRF CUSTOMER contains two routes. Which statement about forwarding for these routes is true?
⚠ Common exam trap
Cisco often tests the distinction between implicit null (label 3) and explicit null (label 0), and the trap here is that candidates assume any route with a label in the VRF table is fully MPLS-switched end-to-end, not realizing that label 3 means the label is popped before the final hop.
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
✓
Traffic to 10.1.1.0/24 will be label-switched with an implicit null label.
The output shows that for the VRF CUSTOMER, the route to 10.1.1.0/24 has a next hop of 192.168.1.2 and is associated with label 3 (implicit null). In MPLS L3VPN, label 3 instructs the upstream router to pop the MPLS label and forward the packet using IP routing to the directly connected next hop. Therefore, traffic to 10.1.1.0/24 will be label-switched with an implicit null label, meaning the label is removed before forwarding to the CE router.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Both routes are reachable via MPLS.
Why it's wrong here
10.2.2.0/24 has no label, so it is not reachable via MPLS.
- ✓
Traffic to 10.1.1.0/24 will be label-switched with an implicit null label.
Why this is correct
'Pop' means implicit-null label (label 3), which is popped by the penultimate hop.
- ✗
Traffic to 10.2.2.0/24 will be forwarded using the BGP next hop label.
Why it's wrong here
The BGP next hop (192.168.2.2) does not have a label in the LFIB, so no label is available.
- ✗
Traffic to 10.2.2.0/24 will be forwarded using IP routing.
Why it's wrong here
'No Label' indicates no label is available; the router will drop the packet because it cannot forward in MPLS core without a label.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-501 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 350-501 exam.