Designated Router

Definition of Designated Router

A Designated Router (DR) is a concept in computer networking, specifically in Open Shortest Path First (OSPF) routing protocol. It is a router elected among all the routers in an OSPF network to reduce network traffic and resource consumption. The DR is responsible for generating and distributing Link State Advertisements (LSAs) for the connected networks, ensuring efficient exchange of routing information between routers.


The phonetic representation of “Designated Router” using the International Phonetic Alphabet (IPA) is:/dɪˈzɪɡ.neɪ.tɪd ˈruːtər/

Key Takeaways

  1. Designated Router (DR) is a critical component in OSPF networks, responsible for reducing network traffic and efficiently managing link-state advertisements (LSAs) among routers.
  2. The DR acts as a focal point for all routers in a multi-access network segment, consolidating the exchange of routing information and distributing it to other routers in the network.
  3. DR election occurs when OSPF routers are first activated, taking into account factors such as router priority and highest IP address, ensuring that a single DR is chosen for each network segment.

Importance of Designated Router

The term “Designated Router” is important in the realm of network technology, primarily because it is an essential component of optimizing network performance and minimizing broadcast traffic in multi-access networks.

Designated Routers (DRs) are elected routers within a network segment that are responsible for generating and maintaining routing information, specifically for routing protocols like Open Shortest Path First (OSPF) and Intermediate System-to-Intermediate System (IS-IS). By consolidating routing information and updates from multiple routers in a network, DRs reduce the amount of redundant information shared across the network.

Consequently, this helps to conserve bandwidth and system resources, minimize network congestion, and improve overall network stability and efficiency.


Designated Router (DR) is a critical element in the operation and optimization of networking protocols, particularly in ospf network. The primary purpose of a Designated Router is to reduce congestion, ease routing overhead, and improve the efficiency of the network infrastructure. DR achieves this by acting as a central point for exchanging routing information with its connected routers, effectively reducing the burden of each router having to individually broadcast routing information to all other connected devices.

By minimizing the number of redundant messages transmitted across the network, the Designated Router plays a vital role in optimizing network resources, enhancing overall network performance, and saving bandwidth. A key application of the Designated Router is evident in Open Shortest Path First (OSPF) networks. In OSPF, routers establish adjacencies with their neighbors by exchanging routing information to build a comprehensive map of the network.

However, when large OSPF networks with numerous routers are involved, this process can become resource-intensive, leading to network congestion and adverse impacts on performance. In such scenarios, the election of a Designated Router and its backup (Backup Designated Router, or BDR) comes into play. The DR acts as a central information hub and relays routing updates on behalf of other routers.

This process makes the routing information exchange more streamlined and efficient, ensuring reduced traffic overhead and improved network performance, ultimately allowing for congestion-free and robust communication within the OSPF network.

Examples of Designated Router

The Designated Router (DR) is a concept within the Open Shortest Path First (OSPF) routing protocol, which is commonly used in large-scale Internet Protocol (IP) networks. The DR plays an essential role in reducing the protocol’s overhead and enhancing the efficiency of OSPF communication within a broadcast or non-broadcast multi-access (NBMA) network. Here are three real-world examples where DR technology is employed:

Corporate Networks: In large business organizations with multiple locations, OSPF is often used to manage communication between local area networks (LANs) within the intranet, ensuring efficient routing of data. In such cases, the DR helps minimize protocol overhead, reducing the amount of OSPF traffic within the network.

Internet Service Provider Networks: ISPs with extensive networks require an efficient routing mechanism to offer uninterrupted and reliable service to their users. OSPF serves as a widely-used routing protocol to ensure dynamic routing and load balancing. DRs significantly streamline the OSPF communication process, allowing ISPs to deliver consistent high-speed data exchange and optimal routing.

Campus and University Networks: Educational institutions with large networks spread across various buildings and connecting thousands of users require a robust routing protocol to manage data transfers effectively. OSPF, together with DR, enhances network performance and lowers overhead, providing a smooth online experience for students, faculty, and staff.

Designated Router FAQ

What is a Designated Router?

A Designated Router (DR) is a router in a network that is responsible for maintaining the link-state information for an area and creating adjacency with other routers. DR is mainly used in OSPF (Open Shortest Path First) protocol to reduce the amount of routing information that needs to be exchanged between routers in the same network segment.

How is a Designated Router chosen in an OSPF network?

In OSPF, the Designated Router is elected by routers in the same OSPF network segment based on their Router Priority values and Router IDs. The router with the highest Router Priority becomes the DR. If there is a tie in Router Priority, the router with the highest Router ID will be chosen as the DR.

What is the role of a Backup Designated Router (BDR)?

A Backup Designated Router (BDR) is a router that maintains adjacency with all other routers in the network, just like the DR. The primary role of BDR is to take over the responsibilities of the DR if the DR fails or becomes unreachable. BDR is also elected based on Router Priority values and Router IDs.

Why are Designated Routers important in OSPF?

Designated Routers play a crucial role in optimizing OSPF operations. They help reduce the amount of routing information exchanged between routers within the same network segment and prevent unnecessary flooding of link-state updates. Without a DR, all routers in a network segment would need to establish adjacency with each other, which could result in excessive routing traffic and increased CPU utilization on routers.

Can I configure a router to always become the Designated Router in an OSPF network?

Yes, you can configure a router to always be the Designated Router by setting its Router Priority value higher than any other router in the network. However, it is essential to consider the router’s capabilities and resources before making it a DR. A DR should be able to handle the additional processing requirements and maintain stability within the OSPF network.

Related Technology Terms

  • Open Shortest Path First (OSPF)
  • Link-State Advertisement (LSA)
  • Backup Designated Router (BDR)
  • Broadcast Multi-Access Network
  • Router Priority

Sources for More Information

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