What is OSPF?
OSPF (Open Shortest Path First) is an interior dynamic routing protocol that uses Dijkstra’s algorithm to determine the shortest path.
Key Features
- Supports hierarchical routing domains (Area 0 and others)
- Link-State class IGP protocol
- Fast convergence during network changes
How OSPF Works
- Routers exchange LSAs (Link-State Advertisements)
- Build a shared network topology map
- The SPF (Shortest Path First) algorithm calculates optimal routes
Example:
| Network | Cost Path |
|---|---|
| 10.0.1.0/24 | 10 |
| 10.0.2.0/24 | 5 |
| 10.0.3.0/24 | 20 |
OSPF vs RIP Comparison
| Parameter | RIP | OSPF |
| Algorithm | Distance Vector | Link State |
| Convergence Speed | Low | High |
| Scalability | Limited | High |
| VLSM Support | No | Yes |
Where OSPF is Used
- In medium and large enterprise networks
- Within service provider infrastructures
- In cloud and hybrid architectures
FAQ
Does OSPF use TCP?
No. OSPF uses IP protocol number 89 and does not rely on TCP or UDP.
How is it different from IS-IS?
OSPF is more widely adopted, but IS-IS scales better in very large networks.
Conclusion
OSPF remains a reliable backbone for routing due to its speed, flexibility, and scalability.
