350-501 Punt forwarding path Practice Question
A service provider is troubleshooting an MPLS L3VPN where customers behind CE-A cannot reach CE-B. The PE routers are Cisco ASR 9000 series. On PE-A, the show cef vrf CUSTOMER prefix 10.1.1.0/24 command displays 'punt' as the forwarding path. What is the most likely cause?
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 IP prefix is not resolved via an MPLS label in the LFIB
When show cef vrf CUSTOMER prefix 10.1.1.0/24 displays 'punt', it means the prefix does not have a valid MPLS label in the LFIB (Label Forwarding Information Base). In MPLS L3VPN, the PE must push a label for the next-hop PE to forward traffic across the MPLS core. Without a label, the packet is punted to the CPU for further processing, often due to missing label binding or incomplete LDP/IGP synchronization. Option A correctly identifies this issue. Option B is incorrect because MTU issues would cause drops, not punt. Option C is incorrect because missing route-target import would affect route installation in the VRF but not necessarily cause punt for a locally resolved prefix. Option D is incorrect because CE-PE routing protocol (whether OSPF or BGP) is not directly related to MPLS label resolution on the PE.
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 IP prefix is not resolved via an MPLS label in the LFIB
Why this is correct
The IP prefix is not resolved via an MPLS label in the LFIB – this causes the CEF to punt packets to the CPU because the hardware cannot forward them without a label.
- ✗
The MPLS MTU on the interface is too small
Why it's wrong here
MPLS MTU being too small would cause drops, not punt.
- ✗
The VRF is missing the route-target import statement
Why it's wrong here
Missing route-target import would prevent routes from being imported into the VRF, but that would not cause a punt; the prefix might not be present at all.
- ✗
The CE is not running OSPF with the PE
Why it's wrong here
The CE not running OSPF with the PE is irrelevant because PE-CE routing could be static or BGP.
Visual reference
Go deeper
Related to this question
About these practice questions
One of 971 original 350-501 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
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.