DHCP Discover packets are broadcast packets. This means that a DHCP Discover packet which is sent from the client would not reach the DHCP Server , if the server resides on a different network. This is because , routers are required for communication between different networks and routers do not forward broadcast packets. The IP Helper address feature is configured on the router. The feature informs the router the DHCP Servers IP address for the network. So, When the router receives the DHCP Discover packet, it would convert it from broadcast to unicast packet and then send it to the DHCP Server.
