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6.2 Network Devices for Guest
Systems
The Xen hypervisor is able to provide different types of network interfaces to the VM
Guest systems. The preferred network device should be a paravirtualized network inter-
face. This yields the highest transfer rates with the lowest requirements to the system.
Up to eight network interfaces may be provided for each VM Guest.
Systems that are not aware of paravirtualized hardware, may not have this option. To
connect systems to a network that can only run fully virtualized, several emulated net-
work interfaces are available. The following emulations are at your disposal:
• Realtek 8139 (PCI). This is the default emulated network card.
• AMD PCnet32 (PCI)
• NE2000 (PCI)
• NE2000 (ISA)
• Intel e100 (PCI)
• Intel e1000 (PCI)
All the network interfaces are just software interfaces. Because every network interface
must have a unique MAC address, an address range has been assigned to Xensource
that can be used by these interfaces.
TIP: Virtual Network Interfaces and MAC Addresses
The default configuration of MAC addresses in virtualized environments just
creates a random MAC address that looks like 00:16:3E:xx:xx:xx. Normally, the
amount of available MAC addresses should be big enough to get only unique
addresses. However, if you have a very big installation, or if you want to make
sure that no problems arise from random MAC address assignment, you can
also manually assign these addresses.
For debugging or system management purposes, it may be useful to know which virtual
interface in Domain0 is connected to which Ethernet device in a running guest. This
Virtual Networking 47