3com 2948 switches blocking PXE boot
I have recently been getting to know my way around WDS and have found a strange phenomenon with PCs connected to the network through 3com 2948 switches. All of these PCs fail to configure DHCP addresses during the PXE boot process of network boot, prior to launching WDS. If I connect a pre-installed PC to the same switch and boot windows all works fine, no problems with DHCP, no problems connecting to network. Only an issue with PXE booting, and across the whole network, only a problem with the 3com 2948 switches.
I cannot find anything in the switch config to enable or disable anything relating to PXE booting. The problem applies whether configured with VLANs or at factory default settings.
Has anyone else had a similar problem with these switches, and does anyone know a fix?
The switch is now discontinued but I have flashed the firmware to the latest available from 3com's website