Refer to the exhibit. P3 and PE4 are at the edge of the service provider core and serve as ABR routers Aggregation areas are on either side of the core. Which statement about the architecture is true?

Question

Exhibit

Options

• AIf each area is running its own IGP, the ABR routers must redistribute the IGP routing table into
• BTo support seamless MPLS, TDP must be used as the label protocol
• CIf each area is running its own IGP, BGP must provide an end-to-end MPLS LSP
• DTo support seamless MPLS, the BGP route reflector feature must be disabled

• A
  10% (3)
• B
  3% (1)
• C
  74% (23)
• D
  13% (4)

Explanation

In a Seamless MPLS architecture, multiple IGP domains (aggregation areas and the service provider core) exist as separate routing domains with their own label switched paths (LSPs). Since LSPs built by a single IGP cannot span across IGP domain boundaries, BGP Labeled Unicast (BGP-LU, RFC 3107) is used to stitch together the per-domain LSPs into a single end-to-end MPLS LSP. BGP carries labeled routes between the ABR/ASBR routers (like PE3 and PE4), enabling traffic to be forwarded across all domains without exposing interior topology. LDP (not TDP, which is Cisco-proprietary and deprecated) is typically used, and BGP Route Reflectors are still needed - they are not disabled.

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