This error indicates that no DNS servers are available.

Things to try:

• Check that your DHCP server is handing out a DNS server address.

• If you are using a static IP address instead of DHCP, check that you have also configured a DNS server address.

• Check that iPXE client can reach that DNS server. ( routing and lame firewall rules )

• If you are booting over HTTP/HTTPS on a Lenovo machine and get this when trying to fetch autoexec.ipxe it is due to lack of IP settings handover (non standard path info) They need to fix their firmware, possible workarounds is using embedded script to catch this scenario, get IP and retry autoexec inside iPXE.