How Does DHCP Achieve IP Allocation Operation?
DHCP does its job with Messages like many protocol. Here, as we mentined before, DHCP uses DHCP Messages. Let’s see how these DHCP Messages are used in DHCP IP Allocation Operation.
Here, firstly we will explain the main DHCP Messages for a successfulDHCP IP Allocation Operation. In this operation four DHCP Message is used.
Now, let’s see these four DHCP Messages and the other DHCP Messages one by one.
DHCP Discover Message
For IP allocation, firstly, DHCP Client sends a Broadcast DHCP Discover Message. This DHCP Discover Messege ask this question :
There is also one more important flag in DHCP Discover Message. This flag is “Broadcast Flag”. If this flag set to “1”, this means that DHCP Client is waiting Broadcast responses from the DHCP Server. But if it set to “0”, this means that DHCP Client is waiting Unicast responses from the DHCP Sercer. Even if this flag, the DHCP Server acts as its capability. In most cases, the responses of DHCP Server is Unicast.
DHCP Offer Message
All the nodes in the network receive the DHCP Discover Message. But, only the DHCP Server reply to this message with DHCP Offer Message. This DHCP Offer Message is sent as Unicast or Broadcast, according to the Broadcast Flag in DHCP Discover Message and DHCP Server capability.
The meaning of this message is :
• MAC address of DHCP Client,
• IP address of DHCP Server
• MAC address of DHCP Server
• Offered IP address and Subnet Mask