Similar to the OSPF DR, the IS-IS DIS needs to be elected on a broadcast network. However, the OSPF DR is preemptive by default, whereas the IS-IS DIS is not preemptive by default.

Question

Options

• ATRUE
• BFALSE
• C
• D

• A
  79% (27)
• B
  3% (1)
• C
  12% (4)
• D
  6% (2)

Explanation

Option A is marked as the correct answer in this question, but based on standard networking behavior, this appears to be an error in the answer key. The statement as written is actually FALSE, making B the defensible answer.

In standard OSPF operation, the DR election is non-preemptive: once a DR is elected on a broadcast segment, it retains that role until it fails, even if a new router with a higher priority joins the network. In contrast, IS-IS DIS election is preemptive: if a router with a higher interface priority appears, it immediately takes over as DIS without waiting for the current DIS to fail. The question has these behaviors reversed. Option B (FALSE) is correct because the real-world behavior is the opposite of what the statement claims.

Memory tip: Think "IS-IS IS aggressive" -- IS-IS DIS preempts immediately, while OSPF DR is more conservative and stable once elected.

No community discussion yet for this question.