Which routers will become the new DR and BDR if the switch reboots and all routers have to re-establish OSPF adjacencies?

In OSPF (Open Shortest Path First), the election of the Designated Router (DR) and Backup Designated Router (BDR) is crucial for the efficient management of network traffic, especially in broadcast and multi-access networks like Ethernet. The election process is determined by several parameters, specifically router priority and router ID.

When the switch reboots, all routers on that network segment will re-establish OSPF adjacencies and go through the DR/BDR election process anew. Each router participates in this process by sending out OSPF Hello packets, allowing them to learn about each other's OSPF priorities and router IDs.

In this scenario, if Router R4 becomes the DR, it has either the highest OSPF priority among the eligible routers or, in cases of ties, the highest router ID. Similarly, Router R1 must have the next highest priority or router ID, making it the BDR. Therefore, the correct election of DR and BDR indicates that Router R4 is favored in the election as the Designated Router while Router R1 follows as the Backup.

This scenario is essential in understanding the dynamics of OSPF networking and how router roles can change based on network events like reboots.