When you use PXE, client computers use the following ports to connect to this site system server: For PXE requests: UDP ports ...

When you use PXE, client computers use the following ports to connect to this site system server:

For PXE requests: UDP ports 67, 68, 69, and 4011.

For operating system installation: UDP port 69. 

If you use Windows Firewall on this server, Configuration Manager automatically configures rules to allow these ports. If you use other firewalls, you must configure them to allow these ports.

Are you sure that you want to enable PXE support for clients?