All routers in a network enable the SR-MPLS function based on OSPF. By default, when R3 forwards a packet with the destination address 10.0.4.4, its MPLS label is as shown in the figure. Then the…

Question

Exhibit

Options

• A36000-65535
• B100-65535
• C16100-36100
• D16000-65530

• A
  80% (20)
• B
  12% (3)
• C
  4% (1)
• D
  4% (1)

Explanation

In SR-MPLS, the label that R3 uses to forward traffic toward 10.0.4.4 (R4's loopback) is calculated as SRGB_start + Node-SID_index. The label visible in the figure falls in the 36000+ range, which is only consistent with an SRGB starting at 36000 - matching option A (36000–65535) and no other choice.

Why the distractors fail:

• B (100–65535): An SRGB starting at 100 would produce a label of ~104 (100 + SID index 4), far below what the figure shows; also, starting below 16000 conflicts with valid MPLS label allocation practices in Huawei VRP.
• C (16100–36100): SRGB_start 16100 → label ≈ 16104, which doesn't match the figure, and the range is too narrow relative to what's shown.
• D (16000–65530): SRGB_start 16000 → label ≈ 16004, again inconsistent with the figure's label value.

Memory tip: Work backwards - subtract the Node-SID index from the label shown in the figure to recover the SRGB start (Label − SID_index = SRGB_start). The answer choice whose range begins at that calculated start is correct.

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