i5/OS™ needs a way to communicate with its integrated Windows servers. This communication takes place over a point to point virtual Ethernet network. When an integrated server is installed a special virtual network is created between it and a controlling i5/OS partition. This network is called point to point because it has only two endpoints, the integrated server and the iSeries™, and also because, like a virtual Ethernet network, it is emulated within the iSeries and no additional physical network adapters or cables are used. In i5/OS, it is configured as an Ethernet line description with Port Number value *VRTETHPTP.
When you run the Install Windows server (INSWNTSVR) command it will configure a point to point virtual Ethernet.
You may wonder what makes a point to point virtual Ethernet connection different from a virtual Ethernet network. The answer is that point to point virtual Ethernet is configured differently and can only have two endpoints: the iSeries and an integrated server. Point to point virtual Ethernet only supports the TCP/IP protocol, and by default uses restricted IP addresses in private domains, so the addresses are not passed through gateways or routers.
For Integrated xSeries® Server (IXS) and Integrated xSeries Adapter (IXA) attached xSeries servers, these addresses take the form of 192.168.xxx.yyy, where (xxx and yyy can be from 1 to 2 digits.) For example, for an IXS that is defined with hardware resource number LIN03, the IP address will be 192.168.3.yyy.
For iSCSI hardware, these addresses take the form of 192.168.xxx.yyy, where xxx ranges from 100 to 254 and results in a unique class C network. In our example, the i5/OS side of the point to point network will be given the IP address 192.168.100.1, and the Windows side has 192.168.100.2. As you define multiple line descriptions for the same hardware resource, yyy is incremented.
You can allow the INSWNTSVR command to automatically assign these IP addresses or manually configure them to prevent TCP/IP address collisions with other hosts on the system.