Dynamic Host Configuration Protocol (DHCP) is used to assIP's DHCP-enabled clients. The server holds valid TCP/IP configuration parameters, valid IP addresses and time period of the lease offer. When a client needs an IP, it sends a request to the DHCP server. The DHCP server asks the client to send the required parameters and once it receives the parameters, DHCP server sends the acknowledgement which contains the IP address of the client.
It’s a denial of service attack, an attacker sends forged DHCP requests to the server and leases all the available IP’s thus the legitimate clients will not get an IP assigned; or the Attacker may send bogus request/replies luring the client to connect to attacker’s machine instead of valid DHCP server.
Here the attacker sends fake DNS packets to the server, thus causing fake entries in the DNS table for the target website. So when a client sends a request to the website, DNS server resolves the domain to IP using injected DNS records and redirects the user to a Fake or malicious website intended by the attacker.