As shown in the figure is the networking topology of L3VPN Over SRv6 BE. Then R1 and R4 need to allocate which of the following types of SIDs to CE1 and CE2?

Question

Options

• AEnd
• BEnd.X
• CEnd. DT4
• DEnd.T

• A
  9% (3)
• B
  15% (5)
• C
  74% (25)
• D
  3% (1)

Explanation

End.DT4 is the correct SID type for L3VPN over SRv6 because PE routers (R1 and R4) must perform two actions when receiving tunneled VPN traffic: decapsulate the outer SRv6 header, then do a per-VRF IPv4 routing table lookup to forward packets to the correct CE. End.DT4 encodes exactly this behavior - "D" for decapsulation, "T" for table lookup, "4" for IPv4 - making it the standard SID type advertised via BGP between PE routers in an IPv4 L3VPN scenario.

Why the distractors are wrong:

• End (A): A basic node SID - it only signals "deliver to this node" with no VRF/table lookup; it cannot distinguish between VPN instances.
• End.X (B): An adjacency SID used for Layer 3 cross-connects to a specific outgoing interface/next-hop; it's a traffic-engineering primitive, not a VPN forwarding instruction.
• End.T (D): Similar to End.DT4 but for IPv6 table lookup (not IPv4), and it lacks the decapsulation+VRF semantics needed for L3VPN CE attachment.

Memory tip: Read "DT4" as Decap + Table + 4 (IPv4) - if the question involves an IPv4 L3VPN and the word "SRv6," End.DT4 is almost always the egress PE's SID choice.

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