SNMP

Simple Network Management Protocol uses a manager-agent model: a central NMS queries agents in routers, switches, and servers over UDP port 161, while agents send unsolicited trap alerts to the manager on UDP port 162. The MIB (Management Information Base) defines the object identifiers (OIDs) that map to each metric a device exposes. The key exam distinction is version: SNMPv1 and v2c send community strings in cleartext, making them trivially sniffable, while SNMPv3 adds authentication and optional encryption for secure networks. Note that SNMP polls for metrics, while syslog pushes event logs.