EIGRP networks combine both advantages and disadvantages from Distance Vector and Link State algorithms. What concept used in OSPF is missing from EIGRP?

• A. Aggregate Routing
• B. Area Concept
• C. Route Redistribution
• D. Prefix Lists

Answer: (B)

The idea being tested is using a hierarchical structure to scale routing. OSPF organizes networks into areas, with a central backbone area that all other areas attach to. This creates separate, smaller routing databases in each area, reduces the amount of routing information that needs to be processed and flooded, and allows controlled summary and routing between areas.

EIGRP doesn’t implement this area-based hierarchy; it operates in a single routing domain per autonomous system. It can perform efficient routing with DUAL, and you can summarize or redistribute routes, but there isn’t a built-in concept of areas or an area backbone like in OSPF. That makes the area concept the element OSPF uses that EIGRP does not.

So the missing concept is the area concept.