Table of Contents
- 1: What is OSPF?
- 2: What is EIGRP?
- 3: OSPF vs EIGRP: Key Differences
- 4: How OSPF Works (Simplified)
- 5: How EIGRP Works (Simplified)
- 6: When to Use OSPF?
- 7: When to Use EIGRP?
- 8: Example of Basic OSPF Configuration (Cisco IOS)
- 9: Example of Basic EIGRP Configuration (Cisco IOS)
- 10: Conclusion
- Frequently Asked Questions
What is OSPF?
- OSPF (Open Shortest Path First) is a link-state routing protocol developed by the IETF.
- It uses the Dijkstra's Shortest Path First (SPF) algorithm to calculate the shortest path.
- OSPF is an open standard, meaning it works on multi-vendor environments.
- Designed for large enterprise networks with complex hierarchies.
What is EIGRP?
- EIGRP (Enhanced Interior Gateway Routing Protocol) is an advanced distance-vector routing protocol developed by Cisco.
- It uses the DUAL (Diffusing Update Algorithm) to find the best path with rapid convergence.
- Originally a Cisco proprietary protocol but later released as an open standard (limited).
- Preferred in Cisco-heavy environments.
OSPF vs EIGRP: Key Differences
| Feature | OSPF | EIGRP |
|---|---|---|
| Type | Link-State | Advanced Distance-Vector |
| Algorithm | Dijkstra’s SPF | DUAL (Diffusing Update Algorithm) |
| Standard | Open (Multi-vendor) | Cisco Proprietary (Partially Open) |
| Administrative Distance | 110 | 90 (Internal), 170 (External) |
| Metric | Cost (based on bandwidth) | Composite Metric (Bandwidth, Delay, Load, Reliability) |
| Routing Updates | Link-State Advertisements (LSA) | Partial Updates with DUAL |
| Convergence | Fast (with SPF calculation) | Very Fast (with DUAL algorithm) |
| Network Design | Requires hierarchical design (Areas) | No strict hierarchy required |
| Scalability | Highly Scalable | Scalable (Best within Cisco networks) |
| Usage | Large, multi-vendor enterprise networks | Cisco networks, mixed-sized environments |
How OSPF Works (Simplified)
- Routers share LSAs (Link State Advertisements) with neighbors.
- Every router builds a complete topology map of the network.
- The SPF algorithm calculates the best path based on cost.
How EIGRP Works (Simplified)
- Routers exchange routing information with neighbors using EIGRP Hello packets.
- The DUAL algorithm determines loop-free and backup paths.
- Uses a combination of metrics like bandwidth and delay to select the best route.
When to Use OSPF?
- Multi-vendor network environments.
- Large networks requiring hierarchical structure.
- Where open-standard protocols are mandatory.
When to Use EIGRP?
- Cisco-only environments.
- Networks needing fast convergence with less complexity.
- Where advanced path selection metrics are desired.
Example of Basic OSPF Configuration (Cisco IOS)
router ospf 1
network 192.168.1.0 0.0.0.255 area 0Example of Basic EIGRP Configuration (Cisco IOS)
router eigrp 100
network 192.168.1.0 0.0.0.255Conclusion
Both OSPF and EIGRP are powerful dynamic routing protocols with unique features suited for different network environments.
- Choose OSPF for open-standard, hierarchical, and scalable enterprise networks.
- Choose EIGRP for Cisco-dedicated networks requiring fast convergence and flexible metrics.
Understanding their core differences helps network engineers design efficient and stable routing architectures.
Frequently Asked Questions
Can I use OSPF and EIGRP together?
Yes, but you'll need route redistribution to share routes between them.
Which protocol converges faster?
Generally, EIGRP converges faster due to its DUAL algorithm.
Is EIGRP still Cisco proprietary?
It was partially opened, but full advanced features are still Cisco-specific.