An engineer is working to implement segment routing protocol on the customer's core network. Which step should the engineer take before the segment routing is enabled and is running with BGP?

Question

Options

• ASegment routing must be configured with ISIS.
• BSegment routing must be configured with EIGRP.
• CExplicit-null must be configured for all neighbors.
• DMPLS must be configured.

• A
  2% (1)
• B
  2% (1)
• C
  4% (2)
• D
  91% (41)

Explanation

Segment Routing (SR) with BGP (specifically BGP-LU - BGP Labeled Unicast, or SR-BGP) relies on MPLS as the data plane forwarding mechanism. Before SR can be enabled in the BGP context, the MPLS forwarding plane must be operational on the relevant interfaces and nodes. MPLS provides the label switching infrastructure that SR uses to forward packets along SR paths (SRGB - Segment Routing Global Block labels are MPLS labels). Option A (ISIS) is a common IGP used with SR (SR-ISIS), but it is not a prerequisite before enabling SR with BGP specifically. Option B (EIGRP) does not natively support Segment Routing. Option C (explicit-null for all neighbors) is an optional MPLS label disposition configuration, not a prerequisite. MPLS must be enabled first because SR-BGP programs MPLS forwarding entries into the data plane.

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