The all-ones Null Pointer are part of the software interface of the 82557 ethernet controller. https://www.intel.com/content/dam/doc/manual/8255x-10-100-mbps-e

The all-ones Null Pointer are part of the software interface of the 82557 ethernet controller. https://www.intel.com/content/dam/doc/manual/8255x-10-100-mbps-ethernet-controller-software-dev-manual.pdf https://www.intel.com/content/dam/doc/manual/8255x-10-100-mb...