Hi Andreas, you should check if the dhcp request from the client (which are technical bootpc packets are received on the dhcp server. Does the dhcp server have more than one network card? Then check /etc/default/isc-dhcp-server if the dhcp server is listening on all interfaces.
# tcpdump -pnlqte udp and src port bootpc and broadcast You should also see some messages in the log of the dhcp server, for e.g. if the server receives the request but has no free IP addresses. In addition to tcpdump there's also dhcpdump for debugging. -- best regards Thomas