H12-821_V1.0 · Question #782
An ISIS router with an interface priority of 0 cannot participate in DIS election.
The correct answer is B. FALSE. Option B (FALSE) is correct because in IS-IS, an interface priority of 0 does not disqualify a router from DIS election - it simply gives that router the lowest preference. If all routers on a segment have a priority of 0, the DIS is still elected using the tiebreaker: highest…
Question
Options
- ATRUE
- BFALSE
How the community answered
(32 responses)- A28% (9)
- B72% (23)
Explanation
Option B (FALSE) is correct because in IS-IS, an interface priority of 0 does not disqualify a router from DIS election - it simply gives that router the lowest preference. If all routers on a segment have a priority of 0, the DIS is still elected using the tiebreaker: highest SNPA (MAC address) wins.
Option A (TRUE) is wrong because it conflates IS-IS behavior with OSPF behavior. In OSPF, setting priority to 0 explicitly makes a router ineligible to become DR/BDR - but IS-IS has no such exclusion rule; every router remains a candidate regardless of priority value.
Memory tip: Remember "IS-IS is inclusive, OSPF is exclusive." OSPF priority 0 = opt-out; IS-IS priority 0 = lowest preference, but still in the race. When you see an IS-IS question about priority 0, think: someone still has to win, and it might as well be the lowest-priority router if everyone ties.
Topics
Community Discussion
No community discussion yet for this question.