A. when all equipment is manufactured by Cisco
B. when there are multiple paths to destination networks
C. because having multiple routing protocols confuses hackers
D. when migrating from an older Interior Gateway Protocol (IGP) to a new IGP
E. when  using UNIX host - based routers
F. when smaller broadcast domains are desired

A. The multicast sources must register with the RP to form the multicast distribution tree.
B. An RP is required only in networks running Protocol Independent Multicast dense mode (PIM DM).
C. The mu lticast receivers must register with the RP to form the multicast distribution tree.
D. An RP is required only in networks running Protocol Independent Multicast sparse mode (PIM SM).
E. An RP is required only in networks running Protocol Independent Mu lticast sparse - dense mode (PIM - SDM).
F. To form the multicast distribution tree, the multicast sources register with and the receivers join the RP.