300-510 SPRI: Implementing Cisco Service Provider Advanced Routing SolutionsDemo

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QuestionQ61

MPLS and Segment Routing

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Refer to the exhibit. MPLS traffic from 192.168.4.0/24 to 192.168.5.0/24 fails to traverse the link between R4 and R2. The engineer has verified that:

  • Cisco Express Forwarding is enabled on every router.
  • All routers can reach every network through OSPF.
  • MPLS traffic from 192.168.1.0/24 to 192.168.3.0/24 passes normally across the R1-to-R2 link.

Which action resolves the issue?

  • A On router R4, configure the mpls label protocol Idp command on all serial interfaces.
  • B On router R4, remove the mpls ip command on the s/0/0/2 interface.
  • C On router R2, configure the mpls ip command on the s/0/0/4 interface.
  • D On router R2, configure the mpls label protocol Idp command on the s/0/0/4 interface.
Explanation

MPLS must be enabled on both ends of an MPLS-facing link so that LDP can establish neighbor discovery and distribute labels. R4 uses Serial 0/0/2 toward R2, whose corresponding interface is Serial 0/0/4. R2 lacks mpls ip on Serial 0/0/4, leaving that link outside MPLS forwarding. Configuring mpls ip on R2 Serial 0/0/4 enables MPLS/LDP for the R4–R2 path. Cisco documents that the mpls ip setting enables MPLS LDP on the specified interface.

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