Xenserver Networking


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A short description on how Networking works in Citrix Xenserver

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Xenserver Networking

  2. 2. XENSERVER NETWORKING • XenServer Networking Terminology • Types of Networks • How XenServer Handles VM traffic • Management Interface • Bonds and VLANs
  3. 3. XenServer Networking Terminology PIF: This is the object name for a physical network interface. XenServer is based on linux. This means each physical network interface will get the normal linux name ethX. XenServer will create a PIF object and assigned to each ethXdevice. Each PIF will get his unique ID, uuid, to give him an internal identifier. VIF: Virtual machines connect to networks using virtual NICs, known as virtual interfaces. Virtual interfaces let VMs send and receive network traffic. You can assign each virtual interface its own IP address and MAC address. Network: A network is actually a virtual Ethernet switch with bridging functionality. The switch will get a uniqie uuid and name. The basic virtual switch that you will get with a standard XenServer installation acts like a simple physical switch and allows to connect virtual machines to it via their VIF. A virtual switch can provide an uplink via a PIF to create an external network.
  4. 4. TYPES OF NETWORKS • Single-Server Private networks have no association to a physical network interface and can be used to provide connectivity between the virtual machines on a given host, with no connection to the outside world. • Cross-Server Private networks extend the single server private network concept to allow VMs on different hosts to communicate with each other by using the vSwitch. • External networks have an association with a physical network interface and provide a bridge between a virtual machine and the physical network interface connected to the network. • Bonded networks create a bond between two NICs to create a single, high- performing channel between the virtual machine and the network.
  5. 5. VIFs and External Bridge Here we can see nine bridges ( xenbr0 – xenbr9). Xenserver creates a virtual bridge for each PIF attached to the server. The VIFs are connected to xenbr2, which provides external connectivity
  6. 6. How XenServer Handles VM Traffic • The physical NIC is in promiscuous mode; which means that it would accept all the packets flowing on the wire. • The packet is forwarded to the Virtual switch xenbr0 • The switch would look at the destination MAC address and find the VIF to which it is connected. • Once the VIF is determined, the Xenserver then passes it to the Virtual Machine
  7. 7. MANAGEMENT INTERFACE • Defined during Xenserver installation • Used to control Xenserver via XenCenter • Also used during Live Migration and communication between the hosts in a Resource Pool • Putting the management interface on a VLAN network is not supported
  8. 8. If this PIF is also being used as the management port, an IP address needs to be assigned. In this case it’s actually the bridge that has the IP address, not the PIF. Any packet that’s destined for the management IP address will be processed by the bridge, and then the host OSI layers, since the MAC destination on that frame will be that of the bridge. The PIF won’t process the IP packet, since it doesn’t have an IP address assigned. MANAGEMENT INTERFACE
  9. 9. Bonds and VLANS BONDS Technique where two or more NICs are configured together to logically function as one. Used for redundancy and Throughput aggregation Active-backup : Only one NIC would be actively used for traffic and only in case of its failure would an inactive NIC take over Balance-slb (active-active): Traffic load balancing based on the source MAC address of each Virtual Network Interface (VIF) of a guest.
  10. 10. VLANs • To segregate production and development traffic • For each VLAN, a separate bridge is created • VLAN configuration is transparent to the guest VM. Tagging/untagging is taken care by the kernel.
  11. 11. RESOURCES > Understanding XenServer Networking - The Linux Perspective http://support.citrix.com/article/CTX117915 > XenServer VLAN Networking : http://support.citrix.com/article/CTX123489 > How to Configure Network and Bonds for XenServer http://support.citrix.com/article/CTX132002