Imaging is not working in a switched environment

  • Document ID:3587871
  • Creation Date:02-Oct-2006
  • Modified Date:30-Apr-2012
    • Micro Focus Products:
      ZENworks Desktop Management

Environment

Preboot Execution Environment (PXE)
Novell ZENworks for Desktops 3.2 Preboot Services
Novell ZENworks for Desktops 4 - ZfD4
Novell ZENworks for Desktops 4.0.1 - ZfD4.0.1
Novell ZENworks 6.5 Desktop Management - ZfD6.5
Novell ZENworks 7 Desktop Management - ZfD7
Novell ZENworks Imaging
Novell ZENworks PreBoot Services (PXE)

Situation

ERROR: DHCP configuration failed
DHCP Configuration Error appears on workstation attempting to boot via PXE
Imaging is not working in a switched environment
PXE is not working in a switched environment

Resolution

This problem will only affect PXE or preboot clients that are patched directly into an Ethernet switch or router. To correct this problem, perform one of the following:
  • Turn off STP on the switch entirely.
  • Set STP to Port Fast for every port on the network switch where a PXE workstation is attached.

Once the problem is resolved, the link light on the port should change to green almost immediately after a workstation connected to that port is turned on.

Additional Information

An imaging session will be dropped from either a unicast or multicast directed session if either the workstations or server hits the 30 second timeout period without communication from the other. The use of "Port Fast" and improper setup of Spanning Tree Protocol "STP" can cause excessive network traffic, which can eventually cause the imaging session to fail.
The following information related to this issue can be found in thedocumentation.

Spanning tree protocol (STP) is available on certain switches and is designed to detect loops in the network. When a device (typically a network hub or a workstation) is patched into a port on the switch, the switch indicates to the device that the link is active, but instead of forwarding frames from the port to the rest of the network, the switch checks each frame for loops and then drops it. The switch can remain in this listening state from anywhere between 15 to 45 seconds.

The affect of this is to cause the DHCP requests issued by PXE to be dropped by the switch, causing the PXE session to fail.

It is normally possible to see that the STP is in progress by looking at the link light on the switch. When the workstation is off, the link light on the switch is obviously off. When the workstation is turned on, the link light changes to amber, and after a period changes to a normal green indicator. As long as the link light is amber, STP is in progress.

Formerly known as TID# 10072082