Courts IT is building multi-area OSPF with several normal areas for civic buildings. Which backbone rule must the design obey?
Select an answer to reveal the explanation.
Short Explanation
Area 0 is the courthouse main corridor — every wing needs a doorway into that hallway. Normal areas attach to the backbone through an ABR. Floating islands with no path to area 0 break classic multi-area OSPF.
Full Explanation
Courts IT building multi-area OSPF with several normal areas for civic buildings must obey the backbone rule: each normal area connects to backbone area 0 through an ABR. Area 0 is the transit core for inter-area route exchange; ABRs attach non-backbone areas so Type-3 summaries can be correctly imported and exported between areas. Without that attachment pattern, classic OSPF inter-area reachability breaks and disconnected 'island' areas do not behave as a coherent multi-area domain.
Requiring every normal area to peer only with EIGRP and never with OSPF abandons the OSPF design entirely and fails the stem's multi-area OSPF requirement. Confining area numbers to wireless controllers rather than routers misunderstands where OSPF areas exist—on OSPF routers/interfaces, not as a WLC-only construct. Allowing normal areas to float forever with no path to area 0 is the classic broken design: discontinuous areas yield unpredictable or failed inter-area routing in standard OSPF.
Exam caveat: virtual links exist as a remedial tool when a normal area lacks a direct ABR attachment to area 0, but ENCOR fundamentals emphasize proper hierarchical attachment through ABRs rather than treating islands as acceptable. Do not confuse 'normal area' with stub/NSSA option flags; the backbone rule applies regardless. Also remember ABR identity: a router with interfaces in area 0 and another area.
Operational check: map each civic building area to an ABR with one interface/process adjacency into area 0, verify ABR flags in OSPF database output, and confirm inter-area routes appear as Type-3 on remote building routers. Fail a non-backbone link inside one building and ensure other buildings still reach summarized paths via area 0. Reject any proposed design that leaves a courthouse wing as an OSPF island with no backbone path.