Re: SNMP not listening on LAN address

Hello,

Am 22.07.2023 um 05:00 schrieb system@xxxxxxxxx:

I am working on a 170 running V4R4, and trying to configure SNMP so that I can get this machine into my NMS. For some reason I have been completely unable to get it to listen on my LAN interface, despite going through the SNMP redbook and checking that I had everything in place. If I nmap the machine, I cannot see SNMP listening, nor is my NMS able to communicate using the community I have configured.

I assume TCP/IP is up and running. You're able to ping the machine, and also connect via e. g. telnet?

First, check if you see an actual listener in the ports list (netstat *cnn). You can press F14 to change the port list to numeric. If there is no entry for port 161, SNMP isn't running. Or was unable to do a bind() call at startup.

SNMP is UDP. Not sure if nmap can correctly differ between open and closed states for UDP on all OS'?

What I have now is a community and SNMP configuration with *ANY manager address allowed, and the service configured to autostart.

Sounds reasonable. For me on V4R5, a working configuration looks like this:

chgsnmpa syscontact(*none) sysloc(*none) sndauttrp(*no) autostart(*yes) objacc(*read) logset(*no) logget(*no) logtrp(*no) trpmgr(*none)

You can type chgsnmpa, press F4 to prompt (non enter!), and F11 to see the parameter names.

Also, go cfgtcp => 20 => 1 => 2

There I entered just "public" with the following parameters, like this

addcomsnmp com('public') asciicom(*yes) intnetadr(*any) objacc(*read) logset(*no) logget(*no)

Maybe check and compare values. I think, you'll eventually find the culprit.

The QTMSNMP and QTMSNMPRCV jobs are present in QSYSWRK so the service is running, at least it should be.

I agree.

Similarly, starting the trap manager does not expose a service on port 162.

Not sure if you're expected to "see" (in nmap) a listener for a service which is meant to send packets.

Is there something I am doing wrong?

Nothing obvious, yet. Well done! Very detailed description of the steps you took to try and verify! Exemplary!

I have not been able to find any way to tell SNMP to listen on a specific interface so I am at a loss here. Appreciate your guidance!

I don't think there is any obvious way to do so.

:wq! PoC