EIGRP can summarize routes at any router, unlike OSPF which summarizes only at ABRs.
Benefits of summarization:
- Smaller routing tables
- Reduced query scope
- Faster convergence
- Hidden flapping (if one subnet in the summary goes up and down, only the originating router sees it)
Example: A router advertises:
Configure a summary of instead. Downstream routers see one route, not four. If fails, the summary remains valid. Other routers don't need to reconverge.