I have a small DHCP server with a 50 IP scope. When I try to get an IP to my device using Ethernet I get a static IP.
How can I solve this?
A static IP is exactly the opposite of what a DHCP server handles.
You may have a static IP stored in your devices settings, without knowing the device, OS etc, I can't advise how to check.
I don't believe the following is what you're asking, but for clarification if anyone else stumbles upon this:
DHCP servers will allocate an IP address to a certain device for a certain period of time, so disconnecting and reconnecting will likely give you the same dynamic IP address, but this is still able to change after the lease has expired (often 72 hours but completely variable).
Alternatively, DHCP can reserve IP's for specific MAC addresses, so the IP is still dynamically allocated, but it will always be the same one. This is still different to a static IP address however.