Refer to the exhibit. A technician is troubleshooting a connectivity issue and notices that there is no IS-IS adjacency between R1 and R2. What can the technician change to bring the IS-IS adjacency…

Question

Options

• AChange R2's net address to be in the same area as R1.
• BChange R1's is-type to level-2-only
• CChange R1's net address to be in the same area as R2.
• DChange R2's configuration to no longer set the overload bit.

• A
  10% (3)
• B
  55% (16)
• C
  7% (2)
• D
  28% (8)

Explanation

Option B is correct because when one router is configured as level-1-only and the other as level-2-only, they share no common IS-IS level and therefore cannot establish any adjacency - changing R1 to level-2-only gives both routers a shared level (L2) on which to negotiate and form adjacency.

Why the distractors fail:

• A & C are wrong because matching the NET area address only matters for Level 1 adjacencies; if the routers are operating at different levels (L1 vs L2), being in the same area is irrelevant - they still can't talk.
• D is wrong because the overload bit affects whether a router is used for transit routing, but it does not block adjacency formation - neighbors still become adjacent even when the overload bit is set.

Memory tip: Think of IS-IS levels as radio frequencies - two routers must be tuned to at least one same frequency (L1, L2, or both) to communicate. A level-1-only and level-2-only router are on completely different frequencies; no area match or bit flag can bridge that gap.

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