Occasionally, for the purposes of internal testing or continuity, it’s desirable to bring up a server with a duplicate MAC address. It’s a safe enough manoeuvre (so long as these machines operate on different wires) for the brief periods in which I require it but when this scenario involves the installation of a new server via our installroot PXE service, things are trickier.

Our PXE server is configured automagically by spanning map and, effectively, keyed on MAC, so it’s unlikely to present the correct configuration (reliably) when the new host differs from the old one in some way.

The workaround is to override the PXE configuration on the *existing* server (on the basis that you weren’t planning on reinstalling it, anyway, were you?):

!pxeclient.platforms mADD(new_plat_name) /* e.g. sl6_64 */

/* And, if you need to add or remove serial console support: */
!pxeclient.serial_port mSET(ttyS0) /* or () */

Post-PXE, the dhclient component is aware of subnet differences and will ensure your machine receives the correct profile for installation (though, to prevent future confusion, remove this as soon as the installer has done its work!).