If you are handing out DHCP via your router and layer 3 switch, here’s how to add a DHCP reservation to the mix. I’m including the entire DHCP configuration. The reservation section is noted below.
ip dhcp excluded-address 10.251.0.1 10.251.0.99
ip dhcp pool DATA
network 10.251.0.0 255.255.255.0
ip dhcp pool LAB_PC