The segment ID and multicast IP address will be used by logical switches, one per logical switch. Every time a new logical switch is created, a segment ID will be taken from the configured range to be used as a VNI. The segment ID will be used sequentially from the lowest ID. One segment ID will be used for one logical switch and the ID can only be reused if the logical switch is deleted.

In the hybrid and multicast control plane, a multicast group address will also be used when a logical switch is created. However, one multicast IP address can be reused for multiple logical switches; in this case, multiple logical switches will be mapped into a common multicast IP address. Sharing the multicast IP address will flood the BUM traffic to VTEPs not needing them and create unnecessary traffic in the network. Ideally, one multicast group address should be associated to only one logical switch. Similar to the segment ID, the multicast group address will be used sequentially from the lowest multicast address to the highest multicast address, and return to the lowest multicast address when all the address has been used.

Creating an NSX logical switch will be covered in a later recipe in this chapter. The following screenshot shows the segment ID and multicast addresses assigned to logical switches: