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Creating cross-server private networks requires Citrix XenServer Advanced editions or higher.
To learn more about XenServer editions, and to find out how to upgrade, visit the Citrix
website here.
Previous versions of XenServer allowed you to create single-server private networks that allowed VMs running
on the same host to communicate with each other. The cross-server private network feature, which extends the
single-server private network concept to allow VMs on different hosts to communicate with each other. Cross-
server private networks combine the same isolation properties of a single-server private network but with the
additional ability to span hosts across a resource pool. This combination enables use of VM agility features such
as XenMotion live migration and Workload Balancing (WLB) for VMs with connections to cross-server private
networks.
Cross-server private networks are completely isolated. VMs that are not connected to the private network cannot
sniff or inject traffic into the network, even when they are located on the same physical host with VIFs connected
to a network on the same underlying physical network device (PIF). VLANs provide similar functionality, though
unlike VLANs, cross-server private networks provide isolation without requiring configuration of a physical switch
fabric, through the use of the Generic Routing Encapsulation (GRE) IP tunnelling protocol.
Private networks provide the following benefits without requiring a physical switch:
• the isolation properties of single-server private networks
• the ability to span a resource pool, enabling VMs connected to a private network to live on multiple hosts
within the same pool
• compatibility with features such as XenMotion and Workload Balancing
Cross-Server Private Networks must be created on a management interface, as they require an IP addressable
PIF. Any IP-enabled PIF (referred to as a 'Management Interface' in XenCenter) can be used as the underlying
network transport. If you choose to put cross-server private network traffic on a second management interface,
then this second management interface must be on a separate subnet.
If both management interfaces are on the same subnet, traffic will be routed incorrectly.
Note:
To create a cross-server private network, the following conditions must be met:
• All of the hosts in the pool must be using XenServer 6.0 or greater
• All of the hosts in the pool must be using the vSwitch for the networking stack
• The vSwitch Controller must be running and you must have added the pool to it (The pool
must have a vSwitch Controller configured that handles the initialization and configuration
tasks required for the vSwitch connection)
• The cross-server private network must be created on a NIC configured as a management
interface. This can be the primary management interface or another management interface
(IP-enabled PIF) you configure specifically for this purpose, provided it is on a separate
subnet.
For more information on configuring the vSwitch, see the XenServer vSwitch Controller User Guide. For UI-based
procedures for configuring private networks, see the XenCenter Help.
Creating Networks in a Standalone Server
Because external networks are created for each PIF during host installation, creating additional networks is
typically only required to:
• use a private network
• support advanced operations such as VLANs or NIC bonding