Refer to the exhibit. What is the relationship between Router 1 and Router 2?

Question

Exhibit

Options

• ARouter 1 centrally learns the topology of the network to aid in SR-TE path selection, and
• BRouter 1 and Router 2 are participating in SR-TE tunnels and are both head-end routers.
• CRouter 1 and Router 2 centrally learn the topology of the network to aid in SR-TE path
• DRouter 2 is the head-end router in an SR-TE tunnel, and it is learning topology of the network

• A
  2% (1)
• B
  2% (1)
• D
  96% (43)

Explanation

In Segment Routing Traffic Engineering (SR-TE), the head-end router is responsible for initiating and signaling SR-TE tunnels toward a tail-end destination. The head-end router needs full topology awareness to compute or request explicit paths expressed as segment lists (SID stacks). Router 2 is the head-end router that is establishing SR-TE tunnels and is simultaneously learning network topology - typically via BGP-LS (BGP Link-State), which distributes the IGP topology database to BGP speakers, or via a PCE (Path Computation Element). Router 1, in this context, is likely acting as a PCE or BGP-LS route reflector feeding topology to Router 2. A is incorrect because it reverses the roles. B is incorrect because only Router 2 is the head-end. C is incorrect because only one router is centrally learning topology in this described relationship. D correctly identifies Router 2 as the head-end learning topology for SR-TE path computation.

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