CCNP ENCOR reference
EIGRP vs. OSPF Quick Reference
The trust model, metric, and convergence differences tested in ENCOR objective 3.5 — a fit-for-purpose comparison, not a search for a universal winner.
The core difference
EIGRP (advanced distance-vector) trusts summarized information from direct neighbors. OSPF (link-state) floods link information so every router in an area builds an identical, complete topology database and independently runs SPF against it.
EIGRP's DUAL algorithm can pre-compute a feasible successor — a loop-free backup route usable instantly on failure, with no recomputation. This is EIGRP's biggest convergence advantage, but only when a feasible successor actually exists for the topology in question.
When each tends to fit better
EIGRP: simpler configuration, very fast convergence when feasible successors exist, historically Cisco-centric (though opened for limited multi-vendor use).
OSPF: open standard supported broadly across vendors, hierarchical area structure for large or multi-vendor networks, industry-standard choice when interoperability matters more than raw simplicity.
At a glance
| EIGRP | OSPF | |
|---|---|---|
| Category | Advanced distance-vector | Link-state |
| Metric | Composite (bandwidth + delay by default) | Cost (reference bandwidth ÷ interface bandwidth) |
| Fast-convergence mechanism | Feasible successor (pre-computed backup) | SPF recomputation from a shared link-state database |
| Vendor support | Historically Cisco-centric | Open standard, broad multi-vendor support |