DHCP Request Message
DHCP clients send the request message to the server when it receives a DHCP offer message from the server. This message tells the server that it accepts the IP address given by the server. Here destination address will be 255.255.255.255 means it’s again broadcast. The reason for this is there might be many DHCP servers in the network so the client may receive multiple offer messages and it will accept the request that reaches him first and send a broadcast message to eliminate other DHCP servers. Here source IP address will be 0.0.0.0 as the DHCP server hasn’t yet assigned an IP address to the client. DHCP Request Message is also a broadcast message.
Source IP address: 0.0.0.0 Destination IP address: 255.255.255.255 Source MAC address: MAC address of DHCP clients Destination MAC address: MAC address of DHCP server
How DORA Works?
Dynamic Host Configuration Protocol(DHCP) uses the DORA. Dynamic Host Configuration Protocol is the protocol of the application layer. It is used to provide Subnet Mask, Router Address, DNS Address, and Vendor Class Identifier. In fact, DHCP provides an automatic IP address to Hosts which want to connect to a network.
DORA is the process that is used by DHCP. DORA helps in providing an IP address to hosts or client machines. DORA is the process that follows some steps between the server and client. It gets the IP address from the centralized server. It consists of four-stage:
- Discover
- Offer
- Request
- Acknowledge
Now let’s see what happens when DHCP clients request a DHCP server an IP address. Let’s see what messages are exchanged between them in the process.
Note: In the network layer, DHCP messages are always broadcast. In the data link layer also DHCP messages are broadcast.