In OSPF networks, when multiple routers are connected to a shared multi-access broadcast segment (like an Ethernet switch), they undergo an election process to select aDesignated Router (DR)and aBackup Designated Router (BDR). This mechanism is essential for reducing the number of adjacencies and limiting the volume of Link State Advertisement (LSA) flooding on the segment.

The OSPF election process follows a strict hierarchy based on the following criteria:

Interface Priority:The router with the highest OSPF interface priority is elected as the DR. The router with the second-highest priority becomes the BDR. In Junos, the default priority is 128, but it can be manually configured between 0 and 255.

Router ID:If there is a tie in priority, the router with the numerically highest Router ID (RID) wins the election.

Analyzing the configuration provided in the exhibit:

R1:Priority 200, Router-ID 192.168.1.1

R2:Priority 100, Router-ID 192.168.1.2

R3:Priority 50, Router-ID 192.168.1.3

R4:Priority 90, Router-ID 192.168.1.4

Comparing the priority values,R1 has the highest priority (200)and therefore becomes theDR. The next highest priority value among the remaining routers is100, which belongs to R2, making it theBDR. Although R4 has a higher Router ID than R2, the priority value is evaluated first and takes precedence.

Since all routers came online within a short window (one minute), they participate in the same election cycle, ensuring the configured priorities dictate the outcome rather than "first-come, first-served" preemption behavior common in OSPF once a DR is already established.