Session No.21
Session No.21
Session No.21
Session no. 21
DYNAMIC HOST CONFIGURATION PROTOCOL (DHCP)
DHCP MESSAGES
The first time a DHCP client computer attempts to log on to the network, it requests IP address information from a DHCP
server by broadcasting a DHCP Discover packet.
It is a broadcast message where the source IP address in the packet is 0.0.0.0 because the client does not yet have an IP
address and the destination address is 255.255.255.255.
DHCPOFFER
Each DHCP server that receives the client DHCP Discover packet responds with a DHCP Offer packet containing an
unleased IP address and additional network configuration information, such as the subnet mask and default gateway.
More than one DHCP server can respond with a DHCP Offer packet. The client will accept the first DHCP Offer packet
it receives.
DHCPREQUEST
When a DHCP client receives a DHCP Offer packet, it responds by sending a DHCP Request packet that contains the
offered IP address, and shows acceptance of the offered IP address
DHCP Acknowledge (DHCPAck) 7
The DHCPACK message is an acknowledgement by the DHCP server that authorizes the DHCP client to start using the
network configuration it received from the DHCP server earlier.
DHCPNAK
This message is the exact opposite to DHCPACK described above. This message is sent by the DHCP server when
it is not able to satisfy the DHCPREQUEST message from the client.
DHCPDECLINE
This message is sent from the DHCP client to the server in case the client finds that the IP address assigned by
DHCP server is already in use.
DHCPRELEASE
A DHCP client sends a DHCP Release packet to the server to release the IP address and cancel any remaining
lease.