162 SNMP-Trap UDP
Reference for UDP port 162, commonly associated with SNMP-Trap.
What it's for
Port 162 is where SNMP trap messages are received — unsolicited notifications a managed device (router, switch, server) sends to a monitoring system when something noteworthy happens (an interface going down, a threshold being crossed, a hardware fault). It's the inverse direction of port 161's poll-based model: instead of the monitoring system asking "what's your status?", the device proactively reports "something changed."
Protocol basics
Like standard SNMP, traps run over UDP, since a lightweight, connectionless "fire and forget" notification fits the use case better than a persistent connection. Because UDP doesn't guarantee delivery, trap-based monitoring is typically used alongside, not instead of, regular polling on port 161 — a dropped trap won't necessarily be noticed unless something else also detects the underlying condition. SNMPv3 traps ("informs," in SNMP terminology) add acknowledgment and retry behavior that basic v1/v2c traps lack.