OSPF vs EIGRP: Choosing the Right Interior Routing Protocol
Both OSPF and EIGRP can route your internal network well — but they get there very differently. Here is a practical guide to picking the right one for your topology.
When you build a routed network beyond a couple of devices, you need a dynamic routing protocol so routers learn paths automatically. Two of the most common choices inside a single organization are OSPF and EIGRP. Both work well, but they solve the problem differently.
The 30-second summary
- OSPF is an open-standard link-state protocol. It builds a full map of the network and runs Dijkstra's algorithm to find the shortest path. Vendor-neutral.
- EIGRP is a Cisco advanced distance-vector protocol. It converges fast, is simple to configure, and uses bandwidth and delay in its metric.
How they think
OSPF floods Link-State Advertisements (LSAs) so every router in an area shares the same topology database, then each independently computes the best tree to every destination.
EIGRP keeps a topology table of routes learned from neighbors, tracks a successor (best path) and a feasible successor (pre-qualified backup), and uses DUAL to switch to the backup almost instantly when a link fails.
When to reach for OSPF
- Mixed-vendor environments — OSPF runs everywhere, not just Cisco.
- Large hierarchical designs — multi-area OSPF with a backbone (area 0) scales cleanly.
- Certification and standards — OSPF is the industry lingua franca.
When to reach for EIGRP
- All-Cisco networks where you want fast convergence with minimal tuning.
- Unequal-cost load balancing, which EIGRP supports natively.
- Simpler configuration for medium networks without formal area design.
A quick lab to prove it
Spin up four routers in GNS3, configure OSPF on one pair and EIGRP on the other, then pull a link and watch convergence:
show ip ospf neighbor
show ip eigrp topology
You will see EIGRP's feasible successor take over almost instantly, while OSPF reconverges after re-running SPF.
The honest answer
For most modern designs I lean toward OSPF for its portability and clean area model — but on an all-Cisco network that needs dead-simple, fast convergence, EIGRP is hard to beat.
Pick the protocol that matches your hardware, your team's skills, and how big the network will grow.
