Dynamic Host Configuration Protocol

DHCP (Dynamic Host Configuration Protocol) is a standard network protocol used on Internet for dynamically assigning network protocols such as IP Address.
With DHCP, computers request IP addresses and networking parameters automatically from a DHCP server, reducing the need for a network administrator or a user to configure these settings manually.

DHCP works as a DORA process (Discover, Offer, Request and Acknowledge)

• Discover Process- In Discover process, the Client PC in network broadcast the message with 255.255.255.255 for query of an IP address. As this is Broadcast message it reaches the DHCP Server.

• Offer Process- When a DHCP server receives a DHCPDISCOVER message from a client, which is an IP address lease request, the server reserves an IP address for the client and makes a lease offer by sending a DHCPOFFER message to the client. This message contains the client's MAC address, the IP address that the server is offering, the subnet mask, the lease duration, and the IP address of the DHCP server making the offer.

DHCP Process

• Request Process- In response to the DHCP offer, the client replies with a DHCP request, broadcast to the server, requesting the offered address. A client can receive DHCP offers from multiple servers, but it will accept only one DHCP offer. Based on required server identification option in the request and broadcast messaging, servers are informed whose offer the client has accepted. When other DHCP servers receive this message, they withdraw any offers that they might have made to the client and return the offered address to the pool of available addresses.

• Acknowledge Process- When the DHCP server receives the DHCPREQUEST message from the client, the configuration process enters its final phase. The acknowledgement phase involves sending a DHCPACK packet to the client. This packet includes the lease duration and any other configuration information that the client might have requested. At this point, the IP configuration process is completed.The protocol expects the DHCP client to configure its network interface with the negotiated parameters. After the client obtains an IP address, it should probe the newly received address (e.g. with ARP Address Resolution Protocol) to prevent address conflicts caused by overlapping address pools of DHCP servers.

DHCP network can be compromised by using malicious DHCP server. To prevent this we use Technology called DHCP Snooping. It helps in preventing the ports from getting snopped by intruder or attacker.