Final answer:
The Simple Network Management Protocol (SNMP) is commonly used to send alerts to network administrators about events like high CPU utilization on routers. Syslog is another protocol that can notify administrators by sending log messages to a central server for monitoring.
Step-by-step explanation:
Network Protocols for Event Notifications
The protocol commonly used to send unsolicited messages to alert a network administrator of a network event, such as a high CPU utilization on a router, is the Simple Network Management Protocol (SNMP). SNMP can be configured to issue an alert, also known as a trap, when certain predefined thresholds are reached. Another protocol that offers similar functionality is Syslog, which can send log messages detailing various events to a central logging server. Network administrators can set up alerts based on those log messages for real-time monitoring. These tools are essential for proactive network management and ensuring the health and efficiency of a network infrastructure.