300-440 Question 163
Single answerA network engineer is troubleshooting an MPLS network where traffic is not being properly forwarded between two MPLS-enabled routers. The engineer suspects an issue with label distribution. Which protocol is responsible for distributing labels between Label Switch Routers (LSRs) in an MPLS network?
- A
OSPF
- B
BGP
- C
LDP
- D
EIGRP
Show answer and explanation
Correct answer: C
Explanation
In MPLS networks, the Label Distribution Protocol (LDP) is responsible for distributing labels between Label Switch Routers (LSRs). LDP establishes label bindings and ensures that MPLS forwarding paths, known as Label Switched Paths (LSPs), are correctly set up. Other protocols like OSPF and EIGRP are used for IP routing but do not manage label distribution. While BGP can carry labels in specific use cases (e.g., MPLS VPNs), LDP is the primary protocol for general MPLS label distribution.
- A. Incorrect.
OSPF is a link-state routing protocol used for IP routing within an autonomous system, but it does not handle MPLS label distribution.
- B. Incorrect.
BGP is a path-vector protocol used for inter-domain routing and can carry MPLS labels in specific scenarios (e.g., MPLS VPNs), but it is not the primary protocol for label distribution in basic MPLS networks.
- C. Correct.
LDP (Label Distribution Protocol) is the primary protocol used in MPLS networks to distribute labels between LSRs, enabling label switching operations.
- D. Incorrect.
EIGRP is a distance-vector routing protocol used for IP routing, but it is unrelated to MPLS label distribution.