Huawei Technologies Huawei Technologies Huawei Technologies ZTE Corporation In TRILL multi-homing scenario, the concept of virtual RBridge in [TRILLPN], was introduced to address the MAC flip-flopping problem at remote RBridges. Based on virtual RBridge mechanism, Coordinated Multicast Trees (CMT) solution in [CMT] was introduced to solve the related RPF issues. In this document, additional problems are described regarding virtual Bridges members' state synchronization in multi-homing scenario, including virtual RBridge membership auto discovery, pseudo-nickname static configuration consistency check, dynamic pseudo-nickname allocation, CMT configuration synchronization ,LACP configuration and state synchronization, node/link failure detection, MAC table synchronization, DHCP snooping information, and dynamically joined VLANs and multicast groups. To address these problems, a communication protocol among members of a virtual RBridge group should be provided. Requirements for this protocol are also discussed.