You are asked to monitor a network which has a network monitoring system. using the monitoring server, you notice that it is listening on port number 161 for network events. which network monitoring protocol is in use?

 SNMP

Explanation:

SNMP (Simple Network Management Protocol) , which is a very used network monitoring protocol, uses normally UDP as a transport protocol.

It uses the port 161 for listening messages (events) from the network being monitored, as a "well known" port, like port 80 for HTTP and port 21 for FTP, and 162 for "traps" (interrupts when a abnormal condition is detected).