TRILL facilitates loop free connectivity to non TRILL legacy
networks via choice of an Appointed Forwarder for set of VLANs.
Appointed Forwarder provides VLAN level load sharing with active-
standby model. Mission critical operations such as High Performance
Data Centers require active-active load sharing model. Active-Active
load sharing model can be accomplished by representing any given non
TRILL legacy network with a single virtual RBridge. Virtual
representation of the non-TRILL legacy network with a single RBridge
poses serious challenges in multi-destination RPF calculations. This
document presents the required enhancements to build Coordinated
Multicast Trees (CMT) within the TRILL campus to solve related RPF
issues. CMT provides flexibility to RBridges to select desired path
of association to a given distribution tree.