Refer to the exhibits. A network operator is troubleshooting packet loss seen from the R1 loopback interface to the R2 loopback interface over the core network. The operator is attempting to identify

The correct answer is C. PE1 - Gi0/0/0/3 - forwarding label 24001. To trace an MPLS-forwarded path, the operator must examine the Label Forwarding Information Base (LFIB) on PE1. The LFIB maps incoming labels to outgoing interfaces and outgoing (swap/push) labels. Based on the exhibit, the correct next hop from PE1 toward R2's loopback is via in

MPLS and Segment Routing

Question

Refer to the exhibits. A network operator is troubleshooting packet loss seen from the R1 loopback interface to the R2 loopback interface over the core network. The operator is attempting to identify the next leg in the path from PE1. Which interface and label path should the operator investigate next?

Exhibit

Options

APE1 - Gi0/0/0/3 - forwarding label 24002
BPE1 - Gi0/0/0/2 - forwarding label 24002
CPE1 - Gi0/0/0/3 - forwarding label 24001
DPE1 - Gi0/0/0/2 - forwarding label 24001

How the community answered

(31 responses)

A
3% (1)
B
13% (4)
C
77% (24)
D
6% (2)

Explanation

To trace an MPLS-forwarded path, the operator must examine the Label Forwarding Information Base (LFIB) on PE1. The LFIB maps incoming labels to outgoing interfaces and outgoing (swap/push) labels. Based on the exhibit, the correct next hop from PE1 toward R2's loopback is via interface Gi0/0/0/3, swapping to forwarding label 24001. Selecting the wrong interface (Gi0/0/0/2) or the wrong label (24002) would trace a different path and misdirect the investigation. The operator should follow the label entry that matches the known LSP for the R1-to-R2 path, which points to Gi0/0/0/3 with label 24001.

Topics

#MPLS forwarding#MPLS labels#Packet path#Troubleshooting

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