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300-510 Exam - Question 94

Refer to the exhibit.

A network consultant is updating the company’s MPLS solution and configuring several new PE devices to enable full communication among PE devices connected to the network. The updates must ensure the redundancy and scalability of the network. The egress LSR is configured with mpls ldp explicit-null. While configuring the given PE router to be adjacent to the egress LSR, the consultant notices that MPLS forwarding is not working in the network. Which action resolves the issue?

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Correct Answer: B

Configuring Cisco Express Forwarding (CEF) on all routers in the MPLS network is crucial for MPLS forwarding to function correctly. CEF is a prerequisite for most modern Cisco router features, including MPLS. Without CEF, the router wouldn’t be able to perform the necessary label switching operations that MPLS relies on. Therefore, enabling CEF on all routers will resolve the issue where MPLS forwarding is not working.

Discussion

4 comments
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DUsooOption: D
Apr 9, 2024

Why we should configure CEF on all routers in the MPLS network?? MPLS is already running and we want to add only few new PEs routers. What we need is to be open TCP/UDP port 464, which is needed for LDP discovery/ session build

a20f227
Apr 29, 2024

If I'm not wrong the LDP port is the 646 and not the 464 listed in answer D.

snowbowOption: B
May 24, 2024

Nothing else makes sense

74ff862Option: B
Jul 18, 2024

B is correct, without CEF, MPLS forwarding won't work.

74ff862Option: B
Jul 19, 2024

B is correct, without CEF, MPLS forwarding won't work.