Virtual Ethernet

Virtual Ethernet allows logical partitions to communicate with each other without having to assign physical hardware to the logical partitions.

You can create virtual Ethernet adapters on each logical partition and connect these virtual Ethernet adapters to virtual LANs. TCP/IP communications over these virtual LANs is routed through the server firmware.

A virtual Ethernet adapter provides similar function as a 1 Gb Ethernet adapter. A logical partition can use virtual Ethernet adapters to establish multiple high-speed interpartition connections within a single managed system. AIX®, IBM® i, Linux, and Virtual I/O Server logical partitions and Windows environments integrated on the System i® platform can communicate with each other using TCP/IP over the virtual Ethernet communications ports.

Virtual Ethernet adapters are connected to an IEEE 802.1q (VLAN)-style virtual Ethernet switch. Using this switch function, logical partitions can communicate with each other by using virtual Ethernet adapters and assigning VLAN IDs that enable them to share a common logical network. The virtual Ethernet adapters are created and the VLAN ID assignments are done using the Hardware Management Console (HMC). The system transmits packets by copying the packet directly from the memory of the sender logical partition to the receive buffers of the receiver logical partition without any intermediate buffering of the packet.

You can configure an Ethernet bridge between the virtual LAN and a physical Ethernet adapter that is owned by a Virtual I/O Server or IBM i logical partition. The logical partitions on the virtual LAN can communicate with an external Ethernet network through the Ethernet bridge. You can reduce the number of physical Ethernet adapters required for a managed system by routing external communications through the Ethernet bridge.

The number of virtual Ethernet adapters allowed for each logical partition varies by operating system.

AIX 5.3 and later supports up to 256 virtual Ethernet adapters for each logical partition.
Version 2.6 of the Linux kernel supports up to 32, 768 virtual Ethernet adapters for each logical partition. Each Linux logical partition can belong to a maximum of 4, 094 virtual LANs.

Besides a Port VLAN ID, the number of additional VLAN ID values that can be assigned for each virtual Ethernet adapter is 19, which indicates that each virtual Ethernet adapter can be used to access 20 networks. The HMC generates a locally administered Ethernet MAC address for the virtual Ethernet adapters so that these addresses do not conflict with physical Ethernet adapter MAC addresses.

After a specific virtual Ethernet is enabled for a logical partition, a network device is created in the logical partition. This network device is named entX on AIX logical partitions, CMNXX on IBM i logical partitions, and ethX on LinuxethX on Linux logical partitions, where X represents sequentially assigned numbers. The user can then set up TCP/IP configuration similar to a physical Ethernet device to communicate with other logical partitions.

If a virtual Ethernet adapter is set for checksum offload, the virtual Ethernet adapter cannot generate a checksum for any packet that the virtual Ethernet adapter sends to a multicast or broadcast MAC address.

Some managed systems contain a Host Ethernet Adapter (HEA). A Host Ethernet Adapter (HEA) is a physical Ethernet adapter that is integrated directly into the GX+ bus on a managed system. HEAs are also known as Integrated Virtual Ethernet adapters (IVE adapters). Unlike most other types of I/O devices, you can never assign the HEA itself to a logical partition. Instead, multiple logical partitions can connect directly to the HEA and use the HEA resources. This allows these logical partitions to access external networks through the HEA without having to go through an Ethernet bridge on another logical partition.

Note: HEA is not supported on POWER8® processor-based server.

You can enable and disable individual virtual Ethernet adapters by using the Hardware Management Console (HMC). You can use the chhwres command to enable or disable a virtual Ethernet adapter. A particular logical partition can be removed from the network when the virtual Ethernet adapter is disabled. You can reconnect the logical partition to the network by enabling the virtual Ethernet adapter. To reconnect the logical partition, you must use a virtual Ethernet that is bridged by using a Shared Ethernet Adapter (SEA) in the Virtual I/O Server (VIOS). The status of the virtual Ethernet adapter can be queried at any time by using the lshwres command. The disabled state persists during partition restart. Trunk adapters cannot be disabled. You must have super administrator or product engineer access to the HMC to enable or disable a virtual Ethernet adapter.

Last updated: Fri, July 05, 2019