NET-SNMP Tutorial -- Using local MIBs

The net-snmp tools can translate numeric object identifies (OIDs) into textual object identifiers using the MIB description files. The net-snmp toolkit provides a few of the standard MIBs, but certainly doesn't contain all the MIBs known to man.

First off, you should know about the paths that the tools load MIBs from. By default, it loads things from the following list of directories:

1. $HOME/.snmp/mibs
2. /usr/local/share/snmp/mibs

So, lets say you have a MIB called CISCO-RHINO-MIB that you want parsed (it really exists, and I particularly liked the name so I'm using it in the tutorial). Place the file in one of the above two directories. If you pulled it from another file (like an RFC), make sure it doesn't contain anything non-MIB related (like the text leading up to it, and the page separators). The very first line in the file should begin with something like "CISCO-RHINO-MIB DEFINITIONS ::= BEGIN"

No, pick a node in the file that you want to translate that currently isn't being translated. From the CISCO-RHINO-MIB, I'll pick the ciscoLS1010ChassisFanLed node.

First, lets verify that our handy snmptranslate command (discussed earlier) doesn't yet know about this node:

% snmptranslate -IR ciscoLS1010ChassisFanLed
Unknown object identifier: ciscoLS1010ChassisFanLed

Nope, it doesn't. So, first we need to download the CISCO-RHINO-MIB.my file and place it in a directory that our snmp tools can find it in. So, I'm going to place the file in $HOME/.snmp/mibs.

Now, lets use the -m flag to snmptranslate to tell it to load that mib. We'll use "-m +CISCO-RHINO-MIB" to indicate that we want the tool to load not only the default set of mibs, but the CISCO-RHINO-MIB as well (the leading '+' plus means "also").

    

snmptranslate -m +CISCO-RHINO-MIB -IR ciscoLS1010ChassisFanLed
Cannot find module (CISCO-SMI): At line 31 in $HOME/.snmp/mibs/CISCO-RHINO-MIB.my
Unlinked OID in CISCO-RHINO-MIB: ciscoLS1010ChassisMIB ::= { workgroup 11 }
Cannot adopt OID in CISCO-RHINO-MIB: ciscoAtmSwitchInvalidCellHeader ::= { ciscoAtmSwitchInvalidCellHeaderEntry 2 }
... rest of output truncated ...
    
  

Wait a minute... What the heck is all that stuff? Errors! Well, the first line is the most important and it's telling us that we're missing the CISCO-SMI MIB as well. So, if we go download that MIB file and place it in our $HOME/.snmp/mibs directory as well the command should suddenly work:

    

snmptranslate -m +CISCO-RHINO-MIB -IR ciscoLS1010ChassisFanLed
.1.3.6.1.4.1.9.5.11.1.1.12
    
  

Success!

One last comment: You can also force loading of a given MIB and its node in one fell swoop (and this method is the one most highly recommended by Niels Baggesen, one of our primary core developers):

    

snmptranslate CISCO-RHINO-MIB::ciscoLS1010ChassisFanLed
.1.3.6.1.4.1.9.5.11.1.1.12
    
  

So, there you have it. A complete example for how to get your own insert-spiffy-mib-here loaded into the net-snmp tools.

Yes, but how do I make it happen all the time?

Good question. And of course, we have multiple options for you. We support a number of ways of doing this.

Note to Ethereal users: One of these methods is how you would have to do it for Ethereal since it won't support the -m and -M options discussed above.

• First, you can put the following lines in a snmp.conf file. This file can be placed in a system-wide location (EG, /usr/local/share/snmp.conf) or in a personal file (EG, $HOME/.snmp/snmp.conf):

  mibs +CISCO-RHINO-MIB
  mibs +SOME-OTHER-SPIFFY-MIB
  	

• You can also use the MIBS environment variable to specify things (example assumes a /bin/sh style shell):

  MIBS=+CISCO-RHINO-MIB:SOME-OTHER-SPIFFY-MIB
  export MIBS
  	

Please note the following sections of the FAQ as well:

• How do I add a MIB
• How do I add a MIB to the tools?
• I'm getting answers, but they're all numbers. Why?
• ... (Read the entire FAQ Please!)