Methods, apparatus and data structures are provided for managing multicast IP flows. According to one embodiment, a network switch module includes a memory and multiple processors partitioned among multiple virtual routers (VRs). Each VR maintains a data structure including information relating to multicast sessions handled by the VR and including a first pointer for each multicast session, a chain of blocks of second pointers and one or more TCBs. Each first pointer points to a chain of blocks of second pointers. Each second pointer corresponds to an OIF of the VR participating in the multicast session defined by the first pointer and defines how many times to replicate packets associated with the multicast session. The TCBs store control information relevant to processing or routing packets. Each second pointer points to a TCB, which identifies the OIF out which packets of the multicast session are transmitted from the VR.