Exam JN0-351 topic 1 question 1 discussion

This is sort of a trick question. Pay attention to the priority and RID values. Priority set to 0 will never become DR or BDR so R1 is excluded. Higher priority is better in OSPF so R2 is lowet than both R3 and R4. R3 and R4 has the same priority so RID will decide. R4 has the highest RID so it will become DR and R3 will then become BDR.

In an OSPF network, the Designated Router (DR) and Backup Designated Router (BDR) are selected based on the router priorities and router IDs (RIDs). The router with the highest priority is chosen as the DR, and the one with the second highest priority is chosen as the BDR. If the priorities are the same, the router with the highest RID is selected. Check Priorities: R3 and R4 both have the highest priority (128). Check Router IDs (RID): Between R3 and R4, R4 has a higher RID (10.10.10.4 vs 10.10.10.3). Therefore: DR (Designated Router): R4 (Priority 128, RID 10.10.10.4) BDR (Backup Designated Router): R3 (Priority 128, RID 10.10.10.3)

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C is correct

C is correct

Priority set to 0 will never become DR or BDR, Same priority so higher RID will be elected as DR so R4, BDR will be R3

R3 Priority 128 second best

When OSPF routers come online simultaneously, the election of the Backup Designated Router (BDR) in OSPF depends on several factors: Router Priority: OSPF routers have a configurable priority value. The router with the highest priority becomes the Designated Router (DR), and the one with the second-highest priority becomes the BDR. If all priorities are equal, the router with the highest router ID becomes the DR, and the second-highest becomes the BDR. Router ID: OSPF uses the router ID as a tiebreaker when priorities are equal. The router with the highest router ID among those routers with the same priority becomes the DR, and the one with the next highest router ID becomes the BDR.

Selected answer C: Because R3 is The BDR and R4 DR

R4 has the highest RID out of the two remaining routers with the same priority

The answer should be A