@Clive_A Thanks for the feedback. It has connected, at least once before. In the meantime I found out the TP Link switch is not to blame as it's not sending that NACK. It's coming from a different...

1. DHCP client broadcasts a DHCP Discover message. The message contains a Requested-IP (50) field which contains an IP which apparently has been previously offered by the server and accepted by the...