Which port is used by the Ident service?

Which port is used by the Ident service?

• A. 23
• B. 113
• C. 161
• D. 25

Answer: (B)

Ident is a user-identification service for TCP connections, and it runs on TCP port 113. When a client connects to a server on this port, the server, if it’s running identd, replies with the identity of the user associated with the connection. This uses TCP to ensure the query and response arrive reliably. Port 113 is the assigned port for this service, which is why it’s the correct choice. Other common ports map to different services: 23 is for Telnet, 161 for SNMP, and 25 for SMTP. Those have unrelated functions, so they aren’t used for identifying the user of a connection.

Ident is a user-identification service for TCP connections, and it runs on TCP port 113. When a client connects to a server on this port, the server, if it’s running identd, replies with the identity of the user associated with the connection. This uses TCP to ensure the query and response arrive reliably. Port 113 is the assigned port for this service, which is why it’s the correct choice.

Other common ports map to different services: 23 is for Telnet, 161 for SNMP, and 25 for SMTP. Those have unrelated functions, so they aren’t used for identifying the user of a connection.