In this post I am going to address a common question about the security and performance impact when multiple logical Layer 2 networks are mapped to one multicast group address.
As mentioned in earlier post here, vCloud Networking and Security (vCNS) Manager is responsible for mapping the logical Layer 2 networks to multicast group addresses. If you provide less number of multicast group addresses than the logical layer 2 networks, vCNS manager will assign the logical layer 2 networks to multicast addresses in a round robin fashion. For example, if there are 4 logical L2 networks (A1,A2,A3,A4) and 2 multicast group addresses (M1, M2), Logical networks A1 and A3 will be mapped to multicast group address M1 while A2 and A4 are mapped to M2.

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