ZEN PXE not working in a VLAN environment

  • 3131242
  • 19-Jun-2007
  • 30-Apr-2012


VLAN switches are being used
Novell ZENworks for Desktops 3.2 Preboot Services
Novell ZENworks for Desktops 3.2
Novell ZENworks 7 Desktop Management Support Pack 1 - ZDM7 SP1 PreBoot Services (PXE)


ZEN PXE not working in a VLAN environment
PXE-e51. No DHCP or BOOTP offers received. Network boot aborted or terminated.


If a workstation gets the DHCP and PDHCP packets in the same VLAN as the DHCP and PDHCP server and it doesn't get the packets in another VLAN, the problem is most likely a switch configuration issue and not a ZEN configuration issue. Getting a packet trace of all packets going to and from the workstation from boot up can help diagnose the issue.
Cabletron switches DO NOT support two DHCP servers. Move the 'normal' DHCP, the PXE DHCP and the TFTP services to one server. NT or Netware can do this.
For a Cisco 3750 48 port switch, try adding the DHCP and PDHCP IP addresses to the iphelper program in the switch.
Just because a workstation is getting an IP address from a DHCP server, doesn't mean that the DHCP packets are coming from the DHCP server. It's possible that the DHCP packets are coming from DHCP server software in the switch itself.

Cisco switches need to have channelling switched off for the DHCP server side. Channeling is enabled by default. Channelling is a port aggregation mode where you would have multiple ports attached to the same device (a server, another switch, etc.) to spread the load

Try putting the PDHCP server on a separate server than the DHCP server. Doing this fixed an issue with a Cisco VLAN switch where IP helper was enabled to forward client DHCP packets to both the DHCP server and the PDHCP server.

For a 29xx series, configuring "SET HOST PORT " will configure the switch ports for having an edge device (workstation/printer/server) attached - it shuts off channeling and enables spantree portfast for the port(s) among other things. Just remember to set speed and duplex and you should be good to go.

Try disabling trunking as a diagnostic measure. It has been known to cause issues with PXE but the exact reasons are unknown at this time. For more info see thislink

Is the LAN card supported? To find out, go to this documentationlink

PortFast has been known to have been switched off and this has caused issues on the PXE boot sequence. PXE tends to boot faster and request DHCP faster than the switch can handle.

PortFast has been enabled so that the Switch can start talking to a device without going through the process of waiting for the switch and device to decide what speed they will communicate, by enabling Portfast the switch will open the port and enable packets to flow.

The normal time period for the Switch to open up a port is around 30 seconds, with PortFast enabled the clients can start talking as soon as they are switched on, and in the case of PXE boot services it would not wait for 30 seconds.

Thedocumentationhas a number of helpful hints on how to setup PXE in a network environment.

Additional Information

Formerly known as TID# 10072029 & NOVL80569