snmptd probe on Linux not binding pm port 162 and not processing any traps

Products

• DX Unified Infrastructure Management (Nimsoft / UIM)
• CA Unified Infrastructure Management On-Premise (Nimsoft / UIM)
• CA Unified Infrastructure Management SaaS (Nimsoft / UIM)

Issue/Introduction

The snmptd probe installed on a Linux server is not processing any traps. A tcpdump shows that the traps are arriving. 

There are no firewall rules blocking the port and "netstat -anp" does not show the snmptd process binding to port 162.

In this environment, the snmptd process is owned by a non-root user with sudo privileges. 

Environment

• DX UIM 23.4.*
• snmptd:  any version
• OS:  any UNIX/Linux system the snmptd probe is certified on

Cause

• The snmptd probe listens by default for incoming traps on port 162. If the probe's process is not owned by root, the probe will not work. 
• An application not running as root cannot bind to port 162 (or any port < 1024) on Linux by default.
• On UNIX/Linux systems, any process that is expected to listen on a particular port needs to have the listening port configured to a port value above 1024.  Since the snmptd probe listens on port 162, it will not work in a 'non-root' context.

Resolution

Possible solutions: 

•  Run the robot the snmptd is running as root user. 
  
  If running the probe as non-root user, ensure the robot is that running with non-root permission to migrate so it run as a root user.
  
  See: Clarifications on Migrating Robot from Non-Root user to Root User on Linux
  
  

OR

• Change default ports:   

1. 1. Change the port that the snmp traps are sent out on the trap sender.
   2. Update the trap_port key in the snmptd probe configuration to listen on a port higher than 1024