PXE problems - PXE client behind firewall not connecting to WDS

[oden08]

I am attempting to connect client workstations behind my PFSense firewall (with private IP's) to my Windows Deployment Server which is in front of the firewall.  I have configured the firewall to use "Network Boot" but it looks as though I am not getting anywhere.

My question is - What settings beyond the network boot section needs to be set to allow PXE clients to get out?

Thanks in advance!