This document is presented as a series of Questions and Answers, discussing various aspects of OSPF protocol designed to prevent inter-area routing loops and related issues. The discussion covers ABR functions, Virtual-Links, OSPF Super-backbone, OSPF Sham-Links, BGP Cost Community. Reader is assumed to know these concepts already, as this publication focuses on complex interaction features arising in MPLS/BGP VPN scenarios. The discussion is culminated by analyzing a number of issues arising in complex multi-area multi-homed OSPF site deployed in MPLS VPN environment. Please download the following document to read the publication: Loop Prevention in OSPF