PXE booting failed with "error: timeout: could not resolve hardware address." for installing Red Hat Enterprise Linux 7

Issue

• We followed the documentation [1] to build the TFTP server for PXE booting.
• I tried to install Red Hat Enterprise Linux 7 with UEFI enabled, so shim.efi and grubx64.efi is used as the boot loader.
• But, it failed with "error: timeout: could not resolve hardware address."

[1] https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Installation_Guide/chap-installation-server-setup.html#sect-network-boot-setup-uefi