I need some information and guidance about SNMP, I am new in development so I need help.
I studied SNMP protocol in detail(MIB,OID, and how it works),
I have some questions
can we change read-only Access of MIB objects to read-write Access?
Can we change Standard MIB to our own requirements?
Thanks and Regards
In a few scenarios, you may change a read-write object to read-only object. But I don't think you can do the opposite.
If you need to meet your own requirements, you may write your own MIB documents and add custom objects. Don't change standard objects, as that breaks the standard.
Related
We are implementing support for the Entity MIB module (RFC 6933) and related MIB modules as part of an SNMP agent (snmpd) using Net-SNMP.
Some of the data is shared between MIB tables and MIB modules, for example table indices and "contained in" objects between entPhysicalTable and entPhysicalContainsTable, and indices between entPhysicalTable and entPhySensorTable.
Note that MIB modules related to the Entity MIB module include the Entity Sensor and Entity Battery MIB modules (RFCs 3433 and 7577 respectively).
Are there any pointers or best practices on how to enable such sharing of data between tables using Net-SNMP?
Is there any built-in support provided by Net-SNMP to achieve this, e.g. any particular mib2c options to construct the relevant template source files for these MIB tables?
In particular, data such as indices needs to be dynamic, as entities such as Field-Replaceable Units (FRUs) may be added or removed whilst an SNMP agent is running.
I note that data (indices) is shared between tables such as ifTable and ifXtable, provided as part of the standard Net-SNMP implementation.
Thanks in advance for any help.
When you run mib2c and specify a table, and don't specify a configuration file, it will ask you questions about the style of code you want to generate. Generally speaking, the choices boil down to whether you want net-snmp to "own" the underlying data store (which you update as values change) or whether you will use your own data structures for the underlying data store (which you will implement hooks to that net-snmp calls to interact with your data). In the former case, net-snmp would handle this "shared data" because it owns it. In the latter case, how you handle it depends on how you organize your data structures.
Mapping some OIDs to system commands is actually all I need
However, I could not find yet a resource which explain how to compose such thing.
Any idea?
There are books about SNMP and MIBs, such as the SNMP MIB Handbook. If you want to learn by example, read some RFCs that define MIBs, such as the Printer MIB.
I read SNMP MIB Handbook. I was a novice of the matter and it lead me inside MIBs very easly. VERY WELL ORGANIZED. Suggested!
I also bought Unserstanding SNMP MIBs, but I didn't read it. After a brief look seems to be very complete.
Good luck!
The Bible of MIBs is considered to be Understanding SNMP MIBs. If you're a book sort of person, that's the recommended reading. The RFCs for MIBS are well worth reading too (RFC2578 through 79) but don't give you a great feel for the corner and "how to" cases.
I am looking for documentation on SNMP IODs return values. For example, the MIB IBM-SYSTEM-HEALTH-MIB 1.3.6.1.4.1.2.6.159.1.1.30 , it provides information on temperature, voltage, and fan status.
1.3.6.1.4.1.2.6.159.1.1.30.3.1.2 provides information on Current State. However, I am not sure what the return values 0 and 3 mean.
Does anyone know where I can find any documentation on these return values for OIDs?
Thanks in advance.
Like lextm-MSFT said, you can find the answer in your vendor's MIB file. If you can't find them on your vendor's support website, Bytesphere (http://www.oidview.com/mibs/vendors.html) is an excellent resource for enterprise MIBs.
You must have the MIB document at hand and check out description section for each objects. Besides, consult IBM support team to see if they have other official documents on that.
I know a little about SNMP, but not enough. I need to develop an application that can read standard SNMP MIBs and read/write the various properties. The network end is no problem, but the actual MIBs and exactly what they may contain is something of a black art to me.
I believe I should be able to use LIBSMI to 'parse' the MIBs, but I don't really understand what the output of the 'parser' is going to be, and how best to use it.
All suggestions welcome...
At the risk of throwing you in the deep end, you might want to take a look at net-snmp. The default installation contains a number of standard mibs with their associated implementation. It also contains a utility (mib2c) that will generate boilerplate code from your mib files.
Once you've read your way through a couple of mibs you should have no trouble familiarising yourself with the way that snmp does things.
Most standard MIB documents were defined in corresponding RFCs published at IETF.
http://www.ietf.org/
Please go to this site to find more details.
Muonics Mib Smithy User Guide provides a good overview of how to build a MIB, which can help you understand the necessary elements for parsing.
You should also look at the ASN.1 ITU specification X.690, because that is the language SNMP is defined in. It also helps if you scour the SNMP RFCs for any Bachus-Naur formatting in the SNMP RFCs. I'm going to suggest you start with RFC3642 and RFC2252.
I'm querying a bunch of information from cisco switches using SNMP. For instance, I'm pulling information on neighbors detected using CDP by doing an snmpwalk on .1.3.6.1.4.1.9.9.23
Can I use this OID across different cisco models? What pitfalls should I be aware of? To me, I'm a little uneasy about using numeric OIDs - it seems like I should be using a MIB database or something and using the named OIDs, in order to gain cross-device compatibility, but perhaps I'm just imagining the need for that.
Once a MIB has been published it won't move to a new OID. Doing so would break network management tools and cause support calls, which nobody wants. To continue your example, the CDP MIB has been published at Cisco's SNMP Object Navigator.
For general code cleanliness it would be good to define the OIDs in a central place, especially since you don't want to duplicate the full OID for every single table you need to access.
The place you need to be most careful is a unique MIB in a product which Cisco recently acquired. The OID will change, if nothing else to move it into their own Enterprise OID space, but the MIB may also change to conform to Cisco's SNMP practices.
It is very consistent.
Monitoring tools depend on the consistency and the MIBs produced by Cicso rarely change old values and usually only implement new ones.
Check out the Cisco OID look up tool.
Notice how it doesn't ask you what product the look up is for.
-mw
The OIDs can vary with hardware but also with firmware version for the same hardware as, over time, the architecture of the management functions can change and require new MIBs. It is worth checking whether any of the OIDs you intend to use are in deprecated MIBs, or become so in the life of the application, as this indicates not only that the MIB could one day be unsupported but also that there is likely to be improved, richer data or access to data. It is also good practice to test management apps against a sample upgraded device as part of the routine testing of firmware updates before widespread deployment.
An example of a change of OID due to a MIB being deprecated is at
http://www.cisco.com/en/US/tech/tk648/tk362/technologies_configuration_example09186a0080094aa6.shtml
"This document shows how to copy a
configuration file to and from a Cisco
device with the CISCO-CONFIG-COPY-MIB.
If you start from Cisco IOS® software
release 12.0, or on some devices as
early as release 11.2P, Cisco has
implemented a new means of Simple
Network Management Protocol (SNMP)
configuration management with the new
CISCO-CONFIG-COPY-MIB. This MIB
replaces the deprecated configuration
section of the OLD-CISCO-SYSTEM-MIB. "
I would avoid putting in numeric OIDs and instead use 'OID names' and leave that hard work (of translating) to whatever SNMP API you are using.
If that is not possible, then it is okay to use OIDs as they should not change per the SNMP MIB guidelines. Unless the device itself changes but that requires a new MIB anyway which can't reuse old OIDs.
This is obvious, but be sure to look at the attributes of the SNMP MIB variable. Be sure not to query variables that have a status of 'obsolete'.
Jay..
In some cases, using the names instead of the numerical representations can be a serious performance hit due to the need to read and parse the MIB files to get the numerical representations of the OIDs that the lower level libraries need.
For instance, say your using a program to collect something every minute, then loading the MIBs over and over is very inefficient.
As stated by others, once published, the name to numerical mapping will never change, so the fact that you're hard-coding stuff into your programs is not really a problem.
If you have access to command line SNMP tools, check out 'snmptranslate' for a nice tool to get back and forth from text to numerical OIDs.
I think that is a common misconception (about MIB reload each time you resolve a name).
Most of the SNMP APIs (such as AdventNet, CMU) load the MIBS at startup and after that there is no 'overhead' of loading MIBs everytime you ask for a 'translation' from name to oid and vice versa. What's more, some of them cache the results and at that point, there is no difference between name lookups and directly coding the OID.
This is a bit similar to specifying an "IP Address" versus a 'hostname'.