Hi Rodrigo,
There are some network requirements for PXE Server. Is your PXE is on the same machine of your DHCP Server, you need to have the Option 60 added on DHCP Server Options. Otherwise, you dont need to change anything at your DHCP Server.
The PXE Server need to see the same packets that are received by the DHCP Server and some router configuration can be necessary. About this you can find more details about this on the folllowing article:
https://www-secure.symantec.com/connect/pt-br/articles/configuring-router-pxe
Please, let us know if this information is what you are looking for.
Regards,