Virtual Ethernet networks are flexible and can be configured in many different ways.

Virtual Ethernet networks that do not include more than one logical partition

Figure 9. System bus, HSL, and iSCSI network tunnels

IXSs, IXA attached systems, and iSCSI HBA attached systems can all participate in virtual Ethernet networks and can communicate with each other.

For IXSs, virtual Ethernet traffic flows over iSeries™ system buses.
For IXA attached hosted systems, virtual Ethernet traffic flows through HSL cables.
For iSCSI attached hosted systems, virtual Ethernet traffic is tunneled through a physical iSCSI network. Virtual Ethernet is needed when an iSCSI network is present for several reasons:
- Virtual Ethernet can work with other virtual Ethernet support in your iSeries server.
- Virtual Ethernet can provide multiple isolated virtual networks through each iSCSI HBA even when switches in the iSCSI network do not support IEEE 802.1Q VLANs
- With IPSec enabled, traffic through an iSCSI network is encrypted. You can think of virtual Ethernet as a powerful Virtual Private Network (VPN). Virtual Ethernet with IPSec can secure an entire virtual network, in contrast to typical VPNs which have just two endpoints
  
  Each iSCSI HBA interface can have two IP addresses, one for storage and one for LAN function, which is used to tunnel virtual Ethernet. i5/OS™ TCP/IP is not aware of these IP addresses. For iSCSI HBAs, virtual Ethernet is tunneled through a physical network with iSCSI HBAs at the physical endpoints.

Figure 10. Two isolated groups of integrated Windows servers on the same iSeries server. Each group has its own virtual Ethernet network.

Figure 10 is intended to help you understand how virtual networks work within the iSeries. There are five separate integrated Windows servers. They are all connected to the single, controlling, i5/OS partition with point to point virtual Ethernet networks (in white). The blue boxes on the bottom of the integrated servers represent physical network adapter cards which allow the machines to make external network connections. The ovals to which they are connected represent external networks. Finally, there are two separate virtual Ethernet networks (in grey). Each integrated server can participate in up to four virtual Ethernet networks simultaneously.

This type of connection is required when configuring a group of integrated servers for clustering.

Like point to point virtual Ethernet, virtual Ethernet networks are configured through Ethernet line descriptions. An integrated server is connected to a virtual Ethernet network when its i5/OS configuration (NWSD) is configured to have an Ethernet line description port number with a value of *VRTETH0 through *VRTETH9. Integrated servers having NWSDs configured with the same port number values are connected to the same virtual Ethernet network. When installing a new integrated server, the Install Windows server (INSWNTSVR) command can automatically create the required line descriptions and assign them IP addresses. In the graphic, the i5/OS side of the line descriptions is not shown. Unlike when you use virtual Ethernet, you should configure a TCP/IP address on the i5/OS side of a line description that is used in a virtual Ethernet network.

Figure 11. Virtual Ethernet tunneled through iSCSI networks

Virtual Ethernet tunneled through iSCSI networks has some special characteristics that are illustrated in Figure 11.

Hosted system 1 can communicate with Hosted system 2 and with Hosted system 3, even though separate iSCSI networks (separate physical switches) are involved.
Virtual Ethernet communication between Hosted system 2 and Hosted system 3 involves the iSeries system, even though both of these hosted systems are connected to the same physical switch.
There is a pair of LAN IP addresses on the physical iSCSI network involved for each hosted system's virtual Ethernet communication. The pair for hosted system 2 and the pair for hosted system 3 have an IP address in common on the i5/OS side.

Virtual Ethernet networks that include more than one logical partition

For the procedure explaining how to create virtual Ethernet networks, see Configure inter-partition virtual Ethernet networks.

Figure 12. A simple, inter-partition virtual Ethernet network.

Now the iSeries has been partitioned, creating three separate virtual i5/OS logical partitions inside the iSeries. Three virtual networks are represented in the graphic; two point to point virtual Ethernet networks (in white) and one virtual Ethernet network (in grey). Each integrated server has a point to point virtual Ethernet network for communicating with its controlling partition. In this example, the virtual Ethernet network has three participants: two integrated servers, each controlled by a different i5/OS partition, and a third partition running i5/OS or other operating system. This is called an inter-partition Ethernet network.

In servers without a Hardware Management Console (HMC), inter-partition connections exist between partitions using the same network number, and integrated servers are connected only if their controlling i5/OS partitions are connected. Network numbers 0-9 are pertinent to integrated servers. For example, if an i5/OS partition is configured for inter-partition connections on networks 1 and 5, then integrated servers controlled by that partition can participate in inter-partition communication on ports *VRTETH1 and *VRTETH5. The procedure to do this is in the iSeries Navigator online help. You can also refer to Logical partition concepts for an overview.

In servers with a Hardware Management Console (HMC), inter-partition connections exist between partitions or integrated servers using the same virtual LAN ID. Participating integrated servers do not support virtual LAN IDs directly. Instead, each participating integrated server needs an Ethernet line description that associates a port value such as *VRTETH1 with a virtual adapter having a virtual LAN ID. You create the virtual adapter using the HMC. For more information, see the Partitioning with an eServer i5 topic and Configuring a virtual Ethernet adapter for i5/OS in the IBM Systems Hardware Information Center. If you migrate inter-partition virtual Ethernet from a server without HMCs to a server with an HMC, you will need to create virtual Ethernet adapters using the HMC and additional Ethernet line descriptions to provide appropriate associations. Note that within the same partition, Windows servers can still communicate with each other by simply using the same virtual Ethernet port number.