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How do SNMP sensors work with a remote probe and core server structure?



Good morning

We have a single core PRTG server with several remote probes installed on servers behind routers and firewalls on separate subnets.. We have around 700 sensors all working fine (monitoring things like SQL databases, services, server memory & HDD space etc) but when I add SNMP sensors they always fail to connect.

If I add SNMP sensors to devices on the same network as the core server everything works as it should do.

My question is that, even with a remote probe installed on a remote server, do I need to open port 161 (and 162?) on the firewall to allow SNMP communication with the core server?

Many thanks, Mark

prtg remote-probe snmp

Created on Jul 26, 2013 9:30:26 AM

6 Replies



Dear Mark, no, the target does not need communicate with the Core Server but with the Remote Probe. Therefore you do not need to open SNMP ports between the Core and the Remote Probe site.
You just have to make sure the machine running the probe can communicate with the target device.
Best regards

Created on Jul 26, 2013 9:35:54 AM by  Konstantin Wolff [Paessler Support]



This doesn't seem to be an issue with the core server, respectively the connection therewith. One possibility, however, is that the IP address for the remote probe is not allowed to connect with the target device. Please run our SNMP Tester v5 Beta on the probe machine and try connecting to the device in case (e.g. by running an "Uptime" or a "Walk" test). Does this yield any results?

Created on Jul 26, 2013 9:36:22 AM by  Patrick Hutter [Paessler Support] (7,225) 3 3



Hi both and thank you for your replies.

In this case the remote probe is installed on the target server we wish to monitor. It is a Dell server and we wish to use the SNMP hardware monitoring functionality of PRTG. The fact that the remote probe is installed on the same server as we are trying to monitor should mean this would work, wouldn't it?

Patrick - I have run an uptime test using the tester you suggested on the target server and it works fine.

Created on Jul 26, 2013 9:48:15 AM



Please also run a "Walk" test using base OID Then, please forward us the resulting log file to [email protected], with reference to this thread.

Created on Jul 26, 2013 11:28:48 AM by  Patrick Hutter [Paessler Support] (7,225) 3 3




I am not clear what information needs to be entered into the "Walk" box - could you advise?


Created on Jul 26, 2013 11:55:12 AM



Merely enter and run the walk. This should yield a list of resulting OIDs that are available on the device. Please forward us this list.

Created on Jul 26, 2013 11:59:53 AM by  Patrick Hutter [Paessler Support] (7,225) 3 3

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