check-mk and snmp

While initializing my Checkmk instance, I encountered a few problems. Here are some tips for future reference.

Tip 1: Sometimes a full scan does not return any data. Here is how to debug the problem on the command line. Make sure you are using the correct Checkmk user; running the command as root does not work.

cmk --debug -vI HOST

…

ERROR: Cannot fetch system description OID .1.3.6.1.2.1.1.1.0. This might be OK for some bogus devices. In that case please configure the ruleset "Hosts without system description OID" to tell Check_MK not to fetch the system description and system object OIDs.

To make this work under “Access to Agents,” add a rule for “Hosts without system description OID.” Specify the hostname, and the SNMP scan should then work.