5 Common MIB Issues

Even if SNMP traps are being properly sent from an agent, a SNMP manager with any of the following MIB issues will create errors and reduce your network visibility, increasing the chance of a costly outage.

1) Needed MIB Not Compiled Onto Your SNMP Manager

Essential SNMP: What is the MIB?
The MIB lists the unique object identifier (OID) of each managed element in an SNMP network. Your SNMP manager can't monitor your devices unless it has compiled their MIB files. The MIB is also a guide to the capabilities of your SNMP devices. For example, if your device's MIB lists OIDs for Traps but not for GetResponse messages, you know it will report alarms, but will not respond to alarm polls. Before compiling, MIBs can be modified in any text editor, such as Notepad or Wordpad. Learning to read MIBs can be difficult, but it's worth the trouble.

A MIB file is a sort of "codebook" that is required to interpret traps sent from your SNMP devices. Without the appropriate MIB, your SNMP manager will not be able to handle incoming traps from an SNMP device.

Remember that:

  • MIB files are generally available from your device
    manufacturer
  • You must compile any new MIBs into your SNMP
    manager
  • In some cases, device manufacturers will not provide MIBs for their devices. This is typically an attempt to force purchases of their proprietary SNMP manager or other equipment. One good way to work around this issue is to use a device that accepts manual input of trap values, such as the T/Mon NOC.

2) Incompatible MIBs

The two most common MIB types are DOS MIBs and UNIX MIBs. DOS MIBs may not work with a UNIX SNMP manager, and vice versa. Check to be sure that you are using MIBs that are compatible with your manager.

3) Missing Reference MIBs

Most main MIBs require additional reference (RFC) MIBs during compiling. If any of these RFC MIBs are missing, the main MIB will not compile properly. When compiling a MIB on DPS Telecom's T/Mon NOC, an error message is added to the MIB Manager log that indicates which MIB files are missing. You may access this log from the Report Viewer. Error reporting on other SNMP managers will vary, but you can always get a list of required reference MIBs by reading the main MIB.

DPS-MIB-V38 DEFINITIONS ::= BEGIN
IMPORTS
  DisplayString
      FROM RFC1213-MIB
  OBJECT-TYPE
      FROM RFC-1212
  enterprises
      FROM RFC1155-SMI;