Difference between OSPF and BGP

In this tutorial, you’ll learn the differences between OSPF (Open Shortest Path First) and BGP (Border Gateway Protocol), including their workings, routing policies, and how they select the best data transmission path.


  1. What is OSPF?
  2. What is BGP
  3. Difference between OSPF and BGP

What is OSPF?

OSPF stands for Open Shortest Path First. It’s a routing protocol used in IP networks, designed to find the shortest path between routers and thus determine routes for routing IP packets. OSPF is widely used within larger networks, such as corporate networks, internet service provider networks, and large enterprise networks.

Key features of OSPF include:

  • OSPF operates as a link-state routing protocol, exchanging information about network reachability and link status.
  • OSPF dynamically calculates the shortest path between routers based on metrics such as link bandwidth.
  • OSPF networks can be divided into areas to improve efficiency and reduce routing overhead.
  • OSPF supports a hierarchical network design with routers organized into areas, including a backbone area.
  • OSPF is scalable and capable of managing large and complex networks.
  • OSPF quickly adapts to network topology changes, ensuring efficient route calculation.
  • OSPF uses a cost-based metric to determine the best path to a destination, based on the bandwidth of links.


What is BGP?

BGP stands for Border Gateway Protocol. It is a standardized exterior gateway protocol used to exchange routing and reachability information between autonomous systems (ASes) on the Internet.

Key features of BGP include:

  • It uses a Path Vector Protocol to maintain routing information, including the AS path to reach a destination.
  • BGP allows administrators to define routing policies based on various attributes such as AS path, prefix length, and others.
  • BGP operates over TCP (Transmission Control Protocol) on port 179, ensuring reliable communication.
  • It is highly scalable, capable of handling large and complex routing tables in the global Internet.
  • BGP provides rich policy controls, giving operators detailed control over routing decisions and policies.
  • BGP ensures stable and efficient routing information exchange, critical for maintaining connectivity on the Internet.

Difference between OSPF and BGP

Here is the difference between OSPF and BGP:

Parameter OSPF BGP
Protocol Type Interior Gateway Protocol (IGP) Exterior Gateway Protocol (EGP)
Routing Scope Within an Autonomous System (AS) Between Autonomous Systems (ASes)
Path Calculation Shortest Path First (SPF) Path Vector Algorithm
Metric Cost (typically based on bandwidth) Administrative Distance
Topology Updates Link state updates Reachability updates
Hierarchy Supports areas and backbone area Hierarchical structure, no area concept
Routing Policy Typically simpler, based on local network Highly flexible, supports complex policies
Protocol Operation Uses flooding for link state updates Uses TCP for reliable communication
Port Number It works in 89 port number It works in 179 port number
Security Mechanisms Authentication, area borders, SPF Authentication, route filtering
Network Size Suitable for medium to large networks Suitable for large-scale networks
Use Case Corporate networks, ISPs ISPs, connecting different ASes
Convergence Time Fast convergence within AS Slower convergence due to larger network
Typical Implementation Internal network routing Internet routing
Example Enterprise network backbone Internet backbone

Key Points to Remember

Here is the list of key points we need to remember about “OSPF & BGP”.

  • OSPF is an Interior Gateway Protocol (IGP) used within Autonomous Systems (AS) to find the shortest path based on link-state updates and cost metrics.
  • BGP is an Exterior Gateway Protocol (EGP) used between ASes on the Internet, employing a path vector algorithm and TCP for reliable communication.
  • OSPF uses the Shortest Path First (SPF) algorithm for path calculation, while BGP uses the Path Vector Algorithm.
  • OSPF operates within an AS, while BGP operates between ASes.
  • OSPF supports areas and a backbone area for hierarchical network design, whereas BGP has a hierarchical structure without the concept of areas.


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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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