I have a small install of PRTG I have been running in a lab environment for evaluation for potential purchase for a much larger network. I have approximately 20 or so sensors.
In a workgroup, using Linux DNS server. DNS is working, has worked, and works well on the network.
Started to get Ping alerts basically due to DNS Lookup failures and I have no idea why. It isn't all the time, but sometimes. I finally decided to look into it more today. For those sensors I am currently getting active DNS lookup failures (Error 11004), I can execute an nslookup without issue directly from the command line on the server PRTG.
As I was troubleshooting, the ONLY thing I changed was the local probe IP from auto to the actual static IP address. Within about 5 minutes, I got SNMP errors on all of my switchports that have been working just fine up until now.
Getting no response errors. So I changed IP Address for probe back to auto, no change.
Downloaded the SNMP tester and here is the interesting thing - I am able to walk the switch when I use the IP Address, but it says hostname lookup failed when I try to walk by hostname. I am running this from the PRTG server and when it fails lookup, I can again open CMD and complete a successful nslookup.
Does anyone know why this is happening?
Edit: Update - I realized on the tester, I was only trying to connect using hostname - when I added the suffix (not on a domain, on a workgroup, but with the suffix wrkgrp.miller) it walked just fine.
So, what am I missing here, why is SNMP not working then? I have checked the community string, firewall isn't an issue - pretty basic setup.