Dhcp and ftp servers listen for and send network traffic on:
well known ports
registered ports
dynamic ports
ip ports

Well known ports

Explanation:

DHCP server transmit the response to the dynamic host configuration server protocol (DHCP) clients. DHCP default port is 67 and its port number is greater than the user data-gram specific port.

FTP server has its default listen at port 21 and file transition protocol(FTP) uses two transmission control protocol(TCP) connection for communication in the network. FTP passes information in port number 21, which is only used to send control information.

Well known port are use to identify the service of network on the public internet and private internet network. Therefore, port 21 and 67 are the well known ports.

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answeruse the nslookup utility;