Abrer_Wiki

Use DHCP to address automatic IP assignment within a network.

Below is the configuration for DHCP in Cisco's IOS.

R1#sh run | s dhcp
ip dhcp excluded-address 192.168.0.1 192.168.0.49
ip dhcp pool MYNETWORK
   network 192.168.0.0 255.255.255.0
   default-router 192.168.0.1 
R1#

Relays are configured with ip helper-address x.x.x.x to specify which address to forward received DHCP requests. When our RTR forwards a DHCP request out via Relay, it does so with the SOURCE ADDRESS of the INTERFACE the HELPER-ADDRESS command was configured on. When this happens, the DHCP server can look at the SOURCE ADDR of the packet, and know exactly which scope to lease an address from - the same network that source resides in, ofc.