# How Do Two BMSs in the Same Region But Different AZs Communicate with Each Other?

If they are in the same VPC, they communicate with each other through an internal network. If they are on the same subnet of a VPC, they communicate with each other through the layer-2 network. If they are on different subnets of a VPC, they communicate with each other through the layer-3 network. An EIP must be bound to the primary NIC of each BMS so that they can communicate with each other.

Parent topic: Network and Security FAQ