UDP 161
Synopsis
- UDP port 161 is used by SNMP agents for management queries.
- Network devices such as Cisco IOS/IOS-XE/ASA, Juniper Junos, Arista EOS, HP/Aruba and Dell switches listen on 161 for SNMP.
- Server and hypervisor agents include Windows SNMP Service, Net-SNMP (snmpd) on Linux/Unix, and the VMware ESXi SNMP agent.
- Common appliances using SNMP on 161 include HP/Canon printers (JetDirect), APC UPS Network Management Cards, Synology and QNAP NAS, MikroTik RouterOS, Ubiquiti/UniFi devices, and firewalls from Palo Alto and Fortinet.
- Monitoring tools such as SolarWinds NPM, PRTG, Zabbix, Nagios, LibreNMS, and ManageEngine OpManager query devices on UDP 161.
- Data center gear (e.g., Cisco Nexus, Arista spine/leaf switches) and campus WLAN controllers (Cisco, Aruba) also expose SNMP on 161 for inventory and performance polling.
- Security note: misconfigured SNMP v1/v2c (e.g., “public”/“private” communities) are widely exploited for information disclosure and for reflected/amplified DDoS attacks via UDP/161.
Observed activity
Last 30 days
Detailed chart