Bandwidth refers to the capacity of the network, and it is measured in either Gigabits per second (Gbps) or Megabits per second (Mbps). The bandwidth that's required is based on the amount of data transferred or the throughput required by the virtual machines. Most modern networks are capable of transferring data at 1 Gbps or 10 Gbps. Network adapters that support 40 and 100 Gbps have recently become available.

The number of physical network adapters in each host that are required to support a solution is dependent on the amount of bandwidth required to support virtual machine network traffic, the number of virtual switches required, and the network redundancy requirements.

The following information from the case example in Chapter 3, The Design Factors, is used to help calculate the network bandwidth requirements:

• Cisco switches are used for network connectivity. Separate VLANs exist for management connectivity and production application connectivity

• No more than 20 application servers (or 200 customers) should be affected by hardware failure
• Currently, each physical server contains a single gigabyte network interface card. Peak network usage is 10 Mbps