IFAIU from the Bz, it works better (it does not timeout) if we use the more recent ipxe payload.
I'm verifying this bug our images in 7.3 include:
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.