Based on the information given in the figure, which of the following descriptions is correct?

Question

Exhibit

Options

• AThe device type of R1 is Level-1
• BR1 is configured with regional authentication
• CThe device type of R1 is Level-2
• DR1 is configured with routing domain authentication

• A
  9% (2)
• B
  4% (1)
• C
  70% (16)
• D
  17% (4)

Explanation

Option C is correct because the figure's IS-IS configuration output for R1 shows it operating as a Level-2 router, which handles inter-area (routing domain backbone) routing between IS-IS areas - not intra-area routing.

Why the distractors are wrong:

• A is wrong because Level-1 routers are confined to a single IS-IS area and only maintain intra-area topology; the figure's output does not match Level-1 behavior.
• B is wrong because area/regional authentication is tied to Level-1 PDUs (within an area); the configuration shown does not indicate area-level authentication is enabled.
• D is wrong because while routing domain authentication would logically pair with a Level-2 router, the figure shows no domain-level authentication configured on R1.

Memory tip: Think of IS-IS levels like a building - Level-1 routers are workers on a single floor (one area), while Level-2 routers are the elevators connecting floors (the backbone routing domain). If a device only handles inter-area traffic, it's Level-2.

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