Physical and logical networks
A physical network connects two or more physical network interfaces.
As stated in the previous section, configuring multiple TCP/IP-based networks helps to prevent cluster partitioning. PowerHA® SystemMirror® communicates across the storage network when necessary. This additional communication path helps prevent partitioned clusters by providing additional communications paths in cases when the TCP/IP-based network connections become congested or severed between cluster nodes.
A logical network is a portion of a physical network that connects two or more logical network interfaces or devices. A logical network interface or device is the software entity that is known by an operating system. There is a one-to-one mapping between a physical network interface/device and a logical network interface/device. Each logical network interface can exchange packets with each logical network interface on the same logical network.
If a subset of logical network interfaces on the logical network needs to communicate with each other (but with no one else) while sharing the same physical network, subnets are used. A subnet mask defines the part of the IP address that determines whether one logical network interface can send packets to another logical network interface on the same logical network.