Cisco Cisco Cisco Bit Index Explicit Replication (BIER) is an architecture that provides optimal multicast forwarding through a "BIER domain" without requiring intermediate routers to run explicit tree-building protocol or to maintain multicast-related, per-flow state. IGP protocols are extended to carry BFR-Id and other encapsulation informations that are used by traditional path computing algorithm using link metric for a loop-free best path selection. This document defines a constrained based path selection using IGP flexible Algorithm for BIER.