Futurewei Futurewei University of Tuebingen University of Tuebingen China Telecom Verizon Inc. This document describes BIER Fast Reroute (BIER-FRR) as a mechanism for Fast Reroute (FRR) in Bit Index Explicit Replication (BIER) networks. It enhances the resiliency of BIER by quickly rerouting BIER traffic in the event of a link or node failure. This ensures that multicast traffic continues to reach its intended destinations, thereby minimizing packet loss and service disruption. BIER-FRR is designed to integrate seamlessly with existing BIER operations without requiring per-flow state or additional signaling. The document suggests additional structures for BIER to hold information for backup forwarding entries and to enable them in case of detected failures. BIER-FRR can implement different protection levels, e.g., link protection or node protection, and different protection strategies. Tunnel-based BIER-FRR and LFA-based BIER-FRR are introduced as protection strategies and their implementation with the proposed extensions. A comparison highlights the differences between both approaches. This document serves as an introductory primer to support future, more comprehensive, BIER Fast Reroute analysis and solution development.