Large EIGRP networks require careful hierarchy and query-boundary design. A structured hierarchical topology with route summarization is one of the most important scaling techniques because summarization reduces routing table size, hides topology changes, and limits the EIGRP query scope when failures occur.
This improves convergence and reduces CPU and bandwidth consumption on routers that do not need detailed route visibility. Implementing multiple EIGRP autonomous systems can also be used as a scaling technique in very large designs because it creates administrative and query boundaries, although it introduces redistribution and policy complexity that must be controlled. Sub-second timers are not a primary scaling method; aggressive timers can increase control-plane load and do not reduce the size of the routing domain. Distribute lists can filter routes, but broad filtering alone is not the core scaling architecture for a network with more than
1000 routers. Modifying delay values influences metric calculation and path selection, not EIGRP domain scale. Therefore, the valid scaling techniques are structured hierarchy with summarization and, where justified, multiple EIGRP autonomous systems.