For my DSL Internet connection I'm using FRITZ!Box Fon WLAN 7170. It works great but unfortunately I could not force it to give particular IP addresses, using DHCP to particular client based on their MACs.
It was possible to configure DHCP to offer a range, let say, 192.168.10.10-20, then first unknown device would get .10, next one .11, and so on. Then via web interface it is possible to make those assignments permanent. But I could not find a way to tell the system that for this MAC I want this IP (and not the one the system already assigned to it).
After some googling the solution was found here.
However it did not work as described: modifying multid.leases did not change anything. After restarting multid the file was generated again. Then solution came from this comment.
Here is a combined solution, taken from the both pages mentioned above, which works for me:
After performing the steps below on the web interface there is some warning: "Changes not supported by the manufacturer". Apart from that everything seems to look the same and it works just fine.