In Which OSPF State is the DR/BDR Election Conducted? A Complete Guide

When preparing for networking certification exams such as CCNA or CCNP, one of the most commonly tested topics is OSPF (Open Shortest Path First) and its state-based neighbor relationship. Among these, a frequently asked question is, “In which OSPF state is the DR/BDR election conducted?”

Understanding the OSPF neighbor states and knowing where the Designated Router (DR) and Backup Designated Router (BDR) elections take place is crucial for passing your exam with confidence. This blog post by DumpsQueen will explain everything you need to know in detail—perfect for exam takers and professionals alike.

Understanding OSPF in Brief

OSPF is a link-state routing protocol used in many enterprise networks due to its fast convergence, scalability, and efficient routing. It divides an autonomous system into areas and shares routing information via LSAs (Link-State Advertisements).

OSPF routers go through various states to establish a neighbor relationship. These include:

Down
Init
Two-Way
ExStart
Exchange
Loading
Full

Each state represents a phase in the OSPF neighbor establishment and database synchronization process.

What is a DR/BDR in OSPF?

In multi-access networks like Ethernet, OSPF uses a Designated Router (DR) and a Backup Designated Router (BDR) to reduce routing traffic.

Here’s why DR/BDR roles are critical:

They reduce flooding of LSAs on broadcast and non-broadcast multi-access networks.
Only the DR and BDR form full adjacencies with all other routers (called DROthers).
They are elected, not manually assigned (unless priority is manually configured).

So, knowing when and where this election happens in the OSPF process becomes very important, especially for exams.

In Which OSPF State is the DR/BDR Election Conducted?

The DR/BDR election is conducted in the "Two-Way" state of OSPF.

Explanation:

Once two OSPF routers reach the Two-Way state, they have mutually recognized each other through Hello packets. This state confirms bidirectional communication, which is essential for neighbor establishment.

For multi-access networks like Ethernet:

When routers reach the Two-Way state, they exchange Hello packets and look at each other's priority values.
Based on the priorities and router IDs, the DR and BDR are elected.

So the answer to the question "in which OSPF state is the DR/BDR election conducted?" is clearly: Two-Way State.

OSPF Neighbor States and Their Role

Let’s break down the OSPF states quickly to understand how they relate to DR/BDR election:

1. Down

No Hello packets have been received.
The router doesn’t know about any neighbors.

2. Init

The router has received a Hello packet, but it hasn’t yet seen itself in the neighbor’s Hello packet.

3. Two-Way

Routers see each other in Hello packets.
This is where DR/BDR election happens on broadcast and non-broadcast multi-access networks.

4. ExStart

The routers decide which one will start the DBD (Database Description) exchange.
Highest router ID wins.

5. Exchange

Routers exchange DBD packets containing summaries of LSAs.

6. Loading

Routers request any missing LSAs using LSR (Link State Request).

7. Full

The routers’ LSDBs (Link-State Databases) are fully synchronized.

DR/BDR Election Criteria

The DR and BDR are elected based on the following:

OSPF Priority (configured on interfaces):

Higher priority wins.
Default is 1.
A priority of 0 means the router cannot be elected as DR or BDR.

Router ID (RID):

If priorities are equal, the router with the higher Router ID becomes DR.

Manual Configuration:

You can influence election by setting priority via the command:
ip ospf priority [value] on the interface.

Persistent Elections:

Once elected, DR and BDR remain so unless a reset occurs.

Example Scenario: DR/BDR Election in Action

Let’s say you have three routers: R1, R2, and R3 connected to the same Ethernet segment.

R1 Priority: 1 | RID: 1.1.1.1
R2 Priority: 1 | RID: 2.2.2.2
R3 Priority: 0 | RID: 3.3.3.3

Election Outcome:

R3 is not eligible.
Between R1 and R2, priorities are the same.
R2 becomes DR (higher RID), R1 becomes BDR.

State where this decision is made: Two-Way.

Common Mistakes and Exam Traps

Many students get confused between the ExStart and Two-Way states. While ExStart is crucial for database synchronization, the DR/BDR election does not happen there.

Also, DR/BDR elections only occur in broadcast and non-broadcast multi-access networks, not in point-to-point or point-to-multipoint topologies.

How to Verify DR/BDR Election on a Cisco Router

To verify the DR/BDR on an interface, use:

bash

show ip ospf neighbor

The output will show neighbor states like:

FULL/DR
FULL/BDR
2WAY/DROTHER

Example output:

nginx

Neighbor ID Pri State Dead Time Address Interface

2.2.2.2 1 FULL/DR 00:00:33 192.168.1.2 Ethernet0

1.1.1.1 1 FULL/BDR 00:00:33 192.168.1.1 Ethernet0

Best Practices for OSPF DR/BDR Configuration

Use priority to influence elections if needed.
Set OSPF priority to 0 for routers that should not become DR/BDR.
Remember, OSPF does not preempt the DR/BDR. A new router with a higher priority won’t become DR unless the current DR fails or the OSPF process is reset.
Always check and confirm DR/BDR roles during troubleshooting.

Conclusion

The answer to the question “in which OSPF state is the DR/BDR election conducted?” is the Two-Way state. This is a critical concept not only for exams like CCNA and CCNP but also for real-world network operations and troubleshooting.

Make sure you understand how the DR/BDR election works, when it happens, and how you can influence it. At DumpsQueen, we’re committed to helping you clear your exams with clarity and confidence.