Two routers running IS-IS can establish an adjacency relationship only if the time interval between IIH sending is the same.

Question

Options

• ATRUE
• BFALSE
• C
• D

• A
  17% (6)
• B
  74% (26)
• C
  3% (1)
• D
  6% (2)

Explanation

Option B is correct because IS-IS does not require matching Hello intervals (IIH sending intervals) for adjacency formation - each router includes its own holding time in the IIH packet itself, and the receiving router simply uses that advertised value to know when to declare the neighbor dead. This means two routers with different Hello intervals can still successfully negotiate and maintain an adjacency. Option A is wrong because it confuses IS-IS behavior with OSPF, where mismatched Hello and Dead intervals do prevent adjacency formation. There is no condition C or D to evaluate here.

Memory tip: Think "IS-IS is Independent" - each side advertises its own hold timer inside the Hello, so neighbors don't need to agree on how often they say hello, only that they keep hearing from each other within the advertised hold time. If you're thinking of a protocol that does require matching timers, that's OSPF, not IS-IS.

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