SR-MPLS is enabled on all routers.

Comprehensive and Detailed In-Depth Explanation:

1. Understanding SR-MPLS (Segment Routing with MPLS):

Segment Routing (SR)leverages MPLS labels to define paths through the network.

The labels representsegments(nodes or specific paths) rather than traditional LDP or RSVP-TE labels.

Thelabel stackdetermines the forwarding path through the network.

Top Label:Determines thenext hop.

Next Label:After label pop, it indicates thesubsequent hop.

2. Analyzing the Given Label Stack:

The label stack encapsulated byR1is as follows:

Layer2:2046

2013

2032

2024

2046

Layer3

Thetop label (2046)indicates that thenext-hop routerisR4.

AfterR4pops the top label, thenext label (2046)directs the packet toR6.

3. Forwarding Path Analysis:

Step 1:R1sends the packet toR2based on internal routing.

Step 2:R2forwards the packet directly toR4as dictated by the top label (2046).

Step 3:R4pops the top label (2046) and checks the next label (again2046), directing the packet toR6.

Step 4:R6receives the packet as the final destination.

4. Why Option B is Correct:

The pathR1-R2-R4-R6matches thelabel stack processingin SR-MPLS.

Thelabels indicate the shortest pathchosen by SR policies, which isR1 → R2 → R4 → R6.

TheSR-MPLS label stackefficiently guides the packet through the optimal path without complex signaling.

Why Other Options Are Incorrect:

Option A (R1-R2-R3-R5-R6):

This path does not match thelabel sequenceas the labels clearly indicate adirect path via R4, not throughR3 and R5.

Option C (R1-R3-R2-R4-R6):

This path is longer and unnecessary, as thelabel stackindicates a moredirect path via R2 and R4.