Housing authority engineers compare how EIGRP and OSPF compute loop-free paths after a topology change. Which contrast is correct at ENCOR depth?
Select an answer to reveal the explanation.
Short Explanation
EIGRP keeps a ready spare tire (feasible successor) via DUAL; OSPF rebuilds the whole map with SPF from the LSDB. That's the path-operation contrast housing IT should remember. Mixing LSA flooding into EIGRP or VLAN IDs into metrics muddies both stories.
Full Explanation
Housing authority engineers comparing EIGRP and OSPF after a topology change should remember this contrast: EIGRP uses DUAL and can install a feasible successor for rapid local backup selection, while OSPF runs SPF against a synchronized link-state database. EIGRP's distance-vector/DUAL behavior keeps loop-free backup candidates when the feasibility condition is met, often avoiding a disruptive query if a successor fails. OSPF instead floods LSAs, updates the LSDB, and recomputes shortest paths with Dijkstra/SPF—fast and consistent, but a different control-plane model than feasible-successor cutover.
Saying OSPF relies only on DUAL feasible successors and never builds an LSDB reverses the protocols: DUAL/FS is EIGRP vocabulary; OSPF is link-state with an LSDB. Claiming EIGRP floods Type-1 LSAs identically to OSPF with no distance-vector behavior erases EIGRP's DUAL/update model and incorrectly assigns OSPF LSA mechanics to EIGRP. Picking paths solely by VLAN ID ignores both protocols' metrics (EIGRP composite metric / OSPF cost) and is not how either installs loop-free routes.
Exam caveat: a feasible successor exists only when reported distance is less than the feasible distance of the successor; without one, EIGRP may query. OSPF has no 'feasible successor' object—convergence is LSA + SPF (and incremental SPF optimizations on platforms). ENCOR wants clean protocol contrast, not mixing LSA types into EIGRP or DUAL into OSPF.
Operational check: on an EIGRP housing router, show topology for a prefix and identify successor vs feasible successor; shut the successor interface and confirm immediate FS install when present. On OSPF, shut a link and observe LSA flood plus SPF recalculation timing rather than FS cutover. Use this contrast when explaining why one civic IGP may fail over locally faster for some prefixes than the other after a distribution uplink loss.