Citrix Provisioning Server Best Practices

Disabling Spanning Tree or Enabling PortFast

  • With Spanning Tree or Rapid Spanning Tree Protocols the ports are placed into a "blocked" state while the switch transmits Bridged Protocol Data Units (BPDU’s) and listens to ensure the BPDU’s are not in a loop-back configuration.
  • The time it takes to complete this "convergence" process depends on the size of the switched network, in which case, PXE may time out.
  • To resolve this issue, disable Spanning Tree on edge-ports connected to clients or enable PortFast or Fast Link depending on the managed switch brand.

Large Send Offload

  • The TCP large send offload option allows the AIX® TCP layer to build a TCP message up to 64 KB long and send it in one call down the stack through IP and the Ethernet device driver. The adapter then re-segments the message into multiple TCP frames to transmit on the wire. The TCP packets sent on the wire are either 1500 byte frames for a MTU of 1500 or up to 9000 byte frames for a MTU of 9000 (jumbo frames).
  • This re-segmenting and storing up packets to send in large frames will cause latency and timeouts to the Provisioning Server. This should be disabled on all PVS Servers and clients.
  • To disable Large Send offload go into the Advance Tab of the NIC Properties.
  • For some NICs there is not setting in the NIC Properties and will require a registry key change to disable it. If the option is not there add the following entry to the registry:

    DWORD = EnableOffload
    Value "0"

Auto Negotiation
Auto Negotiation can cause long booting times and PXE timeouts especially when booting multiple Target Device. It is recommend that all PVS Ports (Server and Client) be hard coded both on the NIC and on the switch.

UPDATE : See the KB at