‘What port does ping use’ is a common networking interview interview question. The answer to the question and the probable questions which can be asked around this topic is explained.
Ping uses ICMP protocol. ICMP works at the network layer of the OSI model. Ping does not use a transport layer protocol. So ping does not use any port number.
If ping does not use a port number, can it communicate with a TCP or UDP based application
The functionality of ping is to test the connectivity at IP layer between systems. It is not used to access TCP or UDP based application.
How can you then block a ping request on a network layer firewall, if it does not have a port number.
Ping uses ICMP at the network layer. ICMP protocol has to be selected on the firewall to allow or deny.
FTP works on TCP port 20 and 21. Since ping does not use a port number, how will a response be recieved if a ping is sent to the FTP server system.
FTP is installed as part of the operating system. The ping request is not recieved by the FTP service, but the TCP/IP protocol which comes installed as part of the operating system. TCP/IP would understand the ping request and would send a response back.
The above question is normally asked for network engineer interviews, network analyst interview, SOC analyst, Security analyst etc. The question is asked to test your fundamental knowledge of the ping protocol and the subsequent questions test your TCP/IP concepts.
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