Configuring Networking

Each managed server has one or more networks. XenServer networks are virtual Ethernet switches that can be connected to an external interface or can be entirely virtual, internal to an individual server or pool. The external interface can be with or without a VLAN tag.

When the XenServer product is installed on a physical server, a network is created for each physical NIC on the server. The network works as a bridge between a virtual network interface on a VM (VIF) and a physical network interface (PIF) associated with a NIC on the server.

When you move a managed server into a pool, these default networks are merged and physical NICs with the same device name are attached to the same network. Typically, you add a network in the following cases:

  • to create an internal network
  • to set up a new VLAN using an existing NIC
  • to create a NIC bond

You can configure up to 16 networks per managed server, or up to 8 bonded network interfaces.

Jumbo frames can be used to optimize performance of traffic on storage networks and VM networks. You can set the Maximum Transmission Unit (MTU) for a new server network in the New Network wizard or for an existing network in its Properties window. The possible MTU value range is 1500–9216.

Network types

There are three different physical network types to choose from when creating a network within XenCenter.

Single-Server private network

This type of network is an internal network that has no association with a physical network interface. It provides connectivity only between the virtual machines on a given server, with no connection to the outside world.

External network

This type of network has an association with a physical network interface and provides a bridge between virtual machines and your external network. The bridge enables VMs to connect to external resources through the server’s physical NIC.

Bonded network

This type of network bonds two or more NICs to create a single, high-performing channel that provides connectivity between VMs and your external network. Three bond modes are supported:

  • Active-active

    In this mode, traffic is balanced between the bonded NICs. If one NIC within the bond fails, all network traffic for the host automatically routes over the second NIC. This mode provides load balancing of virtual machine traffic across the physical NICs in the bond.

  • Active-passive

    Only one NIC in the bond is active. The inactive NIC becomes active if and only if the active NIC fails, providing a hot-standby capability.

  • Link Aggregation Control Protocol (LACP) Bonding

    This mode provides active-active bonding, where traffic is balanced between the bonded NICs. Unlike the active-active bond in a Linux bridge environment, LACP can load balance all traffic types. Two available options in this mode are:

    • LACP with load balancing based on source MAC address

      In this mode, the outgoing NIC is selected based on the MAC address of the VM from which the traffic originated. Use this option to balance traffic in an environment where you have several VMs on the same host. This option is not suitable if there are fewer VIFs than NICs: as load balancing is not optimal because the traffic cannot be split across NICs.

    • LACP with load balancing based on IP and port of source and destination

      In this mode, the source IP address, the source port number, the destination IP address, and the destination port number are used to route the traffic across NICs. This option is ideal to balance traffic from VMs and the number of NICs exceeds the number of VIFs. For example, when only one virtual machine is configured to use a bond of three NICs.


  • Configure vSwitch as the network stack to be able to view the LACP bonding options in XenCenter and to create a LACP bond. Also, your switches must support the IEEE 802.3ad standard.
  • Active-active and active-passive bond types are available for both the vSwitch and Linux bridge.
  • You can bond either two, three, or four NICs when vSwitch is the network stack. However, you can only bond two NICs when a Linux bridge is the network stack.

For more information about the support for NIC bonds in XenServer, see Networking.

Configuring Networking