What is the Difference Between EIGRP and OSPF?

EIGRP (Enhanced Interior Gateway Routing Protocol) and OSPF (Open Shortest Path First) are both interior gateway protocols used for intra-domain routing. They have some key differences in terms of algorithm, scalability, and support for various network applications. Here are the main differences between EIGRP and OSPF:

1. Algorithm: EIGRP is based on the DUAL (Diffusing Update Algorithm) algorithm, while OSPF uses Dijkstra's Shortest Path First algorithm.
2. Convergence Time: EIGRP has a faster convergence time than OSPF due to its algorithm. When a network becomes unreachable from the best path, EIGRP can quickly fall back to the alternate best path. In contrast, OSPF takes a small time to install a new route and re-route traffic once a failure occurs.
3. Scalability: OSPF has higher scalability than EIGRP. EIGRP is complicated and vendor-specific, making it difficult to scale. OSPF, being an open standard, can be easily scaled.
4. Unequal Path Load Balancing: EIGRP supports unequal path load balancing, which helps routers route traffic across links with different speeds. OSPF does not have this feature.
5. Network Application: EIGRP is suitable for small and large networks, while OSPF is more suitable for large networks.
6. Hierarchical Design: OSPF supports hierarchical design, while EIGRP does not.
7. Auto-Summary: EIGRP does not have an auto-summary provision, while OSPF does.

In summary, EIGRP is faster and supports unequal path load balancing, making it suitable for small and large networks. However, it has limitations in terms of scalability and hierarchical design. OSPF, on the other hand, is more scalable, has a hierarchical design, and is suitable for large networks. It also supports auto-summary but does not support unequal path load balancing.

Comparative Table: EIGRP vs OSPF

Here is a table summarizing the key differences between EIGRP and OSPF:

EIGRP is a hybrid protocol that uses features of both distance vector routing and link state routing, while OSPF is a link-state protocol. EIGRP uses the DUAL algorithm and a combination of parameters (bandwidth, load, and delay) to calculate the metric, whereas OSPF uses Dijkstra's algorithm and the interface bandwidth as the metric. EIGRP supports unequal path load balancing, which allows better usage of links at different speeds to forward traffic simultaneously. OSPF does not support this feature. EIGRP has faster convergence time compared to OSPF. EIGRP does not require network partitioning for scalability, while OSPF does.