we have some automatic building of our building machines using packer (jessie, trusty, xenial, macos, ...) on separate network (VLAN on L3 switch which is used as default GW for the network). Till now, the network had some commercial DHCP server and all worked great.
We wanted to switch to our central DHCP which is powered by isc-dhcp, so we did 'ip helper ' command on L3 switch like with any other network which already uses this DHCP server and our building broke. (and of course, we disabled the previous dhcp server)
The reason for that (as far as we debugged it) is that when Linux is installing, it asks for IP using its MAC address as identifier and after installation, it does the some, but with hostname as identifier. So it has different IP during installation and after reboot, when installation finished. Unfortunately, packer checks for IP only once, during installation, so the process cannot complete, because it cannot connect to installed machine.
We cannot set /etc/dhcp/dhclient.conf to use MAC is identifier for some other reasons, so that is not going to be the solution.
The question is: What can i set in isc-dhcp server to behave like the old commercial DHCP server? That server gave the same machine the same ip during and after installation (I guess you just need to pair the hostname in MAC address right?). There wasn't any advanced setting on that server. It allowed you only to specify IP ranges, exclusions, static leases and DHCP options.
Thanks for all your answers
