Virtual Ethernet technology is supported on versions 2.4 and 2.6 of the Linux® kernel on POWER5™ hardware. Virtual Ethernet enables IP-based communication between logical partitions on the same system using a VLAN-capable software switch in POWER5 systems. The bridge module of the Linux kernel, along with the bridge-utils package, enables the logical partitions to communicate with other systems without assigning physical Ethernet slots to the logical partitions.
Virtual networking along with other POWER5 virtualization technologies offers greater flexibility in configuration scenarios. Workloads can be easily consolidated with more control over resource allocation. Network availability can also be improved for more systems with fewer resources using a combination of Virtual Ethernet, the bridge kernel module, and the bonding kernel module. When there are not enough physical slots to allocate a physical network adapter to each LPAR, network access using Virtual Ethernet and the bridge kernel module is preferable to IP forwarding because it does not complicate the IP network topology.
IBM® System p5® and eServer™ p5 hardware supports inter-LPAR communication using virtual networking. 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 (VID) that enable them to share a common logical network. The Virtual Ethernet adapters are created and the VID assignments are done using the Hardware Management Console. The system transmits packets by copying the packet directly from the memory of the sender partition to the receive buffers of the receiver partition without any intermediate buffering of the packet.
The number of Virtual Ethernet adapters for each LPAR varies by operating system. Version 2.4 of the Linux kernel supports up to 100 Virtual Ethernet adapters while version 2.6 of the Linux kernel can support up to 32 768 Virtual Ethernet adapters. Besides a Primary VID (PVID), the number of additional VID 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. To ensure uniqueness among the Virtual Ethernet adapters, the address generation is based on the system serial number, LPAR ID, and adapter ID.
When using the Integrated Virtualization Manager, only PVID is allowed (no additional VLANs), and only the PVID may only be 1-4.
When using Virtual Partition Manager, each partition can have at most one Virtual Ethernet adapter for each PVID from 1-4.
For VLAN-unaware operating systems, each Virtual Ethernet adapter is created with only a PVID (no additional VID values) and the POWER® hypervisor will ensure that packets have their VLAN tags removed before delivering to that LPAR. In the case of VLAN aware systems, such as Linux with the vlan module, you can assign additional VID values besides the PVID and the POWER hypervisor removes the tags of any packets that arrive with the PVID tag. Because the number of Virtual Ethernet adapters supported for each LPAR is large, you can have multiple Virtual Ethernet adapters with each adapter being used to access a single network and therefore assigning only PVID and avoiding the additional VID assignments. This also has the advantage that no additional VLAN configuration is required for the operating system using these Virtual Ethernet adapters.
After a specific virtual Ethernet is enabled for a partition, a network device named ethX is created in the partition. The user can then set up TCP/IP configuration similar to a physical Ethernet device to communicate with other partitions.
Subscribe to this information