I managed to find the problem, and was the firewall. It's necessary to open port 69 UDP for tftp communication.
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Hi,
I've installed the last version (4.5.46) at a WS2008 and checked services ara running. I've also configured the DHCP 066 and 067 parameters in order to make PXE cards work properly. But when I start the computer with PC, it gets a good IP address (shown at DHCP panel), but doesn't get any file from TFTP server, and shows a "TFTP tiemout" message.
Thanks in advance.
Pedro