7.3. Virtual Ethernet
With the help of virtual Ethernet adapters, LPARs can communicate in the network without requiring a physical Ethernet adapter for each LPAR. Each virtual Ethernet adapter is connected to an internal virtual Ethernet switch, which is implemented by the POWER hypervisor. Each virtual Ethernet switch supports the IEEE 802.1q standard (VLANs and QoS). Two LPARs on the same managed system, which are connected to the same virtual Ethernet switch, can communicate with each other directly by the hypervisor; a throughput of over 20 GB/s can be achieved thereby. Figure 7.2 shows this inter-partition communication within a managed system.
PowerVM provides so-called trunking adapters so that LPARs can also communicate with systems outside the managed system. A trunking adapter is a special virtual Ethernet adapter that is connected to a physical Ethernet adapter by a shared Ethernet adapter (SEA) on a virtual I/O server. The shared Ethernet adapter acts as a layer 2 bridge and is implemented in software on the virtual I/O server. Network packets of an LPAR that are directed to an external system are forwarded from the virtual Ethernet switch via a trunking adapter to a virtual I/O server, which then sends the packets to a physical Ethernet adapter with the help of the shared Ethernet adapter and finally forwards the packets to an external network switch.
Figure 7.3 shows the communication path between an LPAR and an external system. The transport route is transparent for the end systems (LPAR and host in the external network).
This chapter initially only deals with the client side of virtual Ethernet. The configuration of shared Ethernet adapters (SEAs) on a virtual I/O server will be discussed in detail later.