We show that the forwarding strategies in the named data networking (NDN) architecture and the original content centric networking (CCN) architecture cannot ensure that Interests return the requested data objects when routing-table loops exist in a stable or dynamic network. We also show that no correct Interest forwarding strategy that allows Interest aggregation can be designed solely on the basis of identifying Interests uniquely in order to detect Interest loops. We introduce SIFAH (Strategy for Interest Forwarding and Aggregation with Hop-Counts). SIFAH prevents or detects Interest loops when Interests are aggregated or forwarded over one or multiple paths. As a result, it is far more efficient than the forwarding strategy in NDN and the original CCN proposal. SIFAH operates by having forwarding information bases (FIB) store the next hops and number of hops to named content prefixes, and by using Interests that state the names of requested content and hop counts that reflect the information in their FIBs.