Exhibit. Which router will become the OSPF BDR if all routers are powered on at the same time?

In OSPF, the Designated Router (DR) and Backup Designated Router (BDR) election on a multi-access broadcast network is determined first by the highest OSPF interface priority, and then by the highest Router ID (RID) if priorities are equal. The default OSPF priority in Junos OS is 128. The phrase "powered on at the same time" is critical because OSPF DR/BDR elections are non-preemptive; simultaneous booting ensures the election strictly follows priority and RID metrics rather than boot order. Based on the standard exhibit topology where all routers share the default priority and have sequential RIDs corresponding to their numbering (e.g., R4 > R3 > R2 > R1), R4 will be elected as the DR (highest RID) and R3 will be elected as the BDR (second-highest RID).

A (R4): R4 possesses the highest Router ID in this topology, which makes it the Designated Router (DR), not the Backup Designated Router (BDR).

B (R1): R1 has the lowest Router ID in the topology, meaning it will become a DROther router, losing the election for both DR and BDR.

D (R2): R2 has the second-lowest Router ID, meaning it will also become a DROther router, as it is outranked by both R4 and R3 during the election.

Juniper Networks Official Documentation: Junos OS Routing Protocols Library, "Understanding OSPF Designated Routers and Backup Designated Routers." (Details the default priority of 128 and the non-preemptive nature of the DR/BDR election process).

IETF RFC 2328 (OSPF Version 2): Section 7.3 (The Designated Router) and Section 9.4 (Electing the Backup Designated Router). DOI: https://doi.org/10.17487/RFC2328. (Provides the vendor-agnostic, foundational protocol standard for how Priority and Router ID dictate the state machine for DR/BDR elections).