I'm new to SNMP. I'm looking at snmp4j's demo AgentX subagent TestSubagent.java (http://www.snmp4j.org/agentX/doc/org/snmp4j/agent/agentx/subagent/test/TestSubagent.html) on a linux box, and have been able to get it registered as a subagent with the snmpd daemon, but I'm unclear how to add new OIDs or alter the value of the existing OIDs that are registered (the 1.3.6.1.4.1.4976 tree). Could anyone point me in the right direction?
You have to register so called ManagedObjects with the DefaultMOServer instance that is used by the sample. There are two major types of ManagedObject: MOScalar and MOTable.
If you have a MIB, you can let AgenPro generate all necessary code. You will only have to put in the instrumentation code then.
Related
I have a list of IP addresses or Cisco router. Now i need to find out, which IP address is assigned to which interface (e.g. i have IP 192.168.1.1 and i need to learn that it is IP address of fa0/0 interface). Which MIB can i use to get the list of IP add with corresponding interfaces via SNMP?
Thanks
I believe the SNMP OID you need for this is 1.3.6.1.2.1.4.34, the object being ipAddressTable from the IP-MIB. See the following URL:
http://tools.cisco.com/Support/SNMP/do/BrowseOID.do?local=en&translate=Translate&objectInput=1.3.6.1.2.1.4.34#oidContent
Cisco has very good SNMP info on their site. The SNMP Object Navigator, or the IOS MIB Locator are your friends. Tons of info there, and you can look at it from any angle you want. For example, provide the router's IOS image filename and see what MIBs it supports, etc.
As far as interfaces and IP address info, that's the most basic of stuff so you will be ok, no need to find any weird MIB for that.
My suggestion would be: make sure SNMP is enabled on the router and an SNMP community is set, jump on a Unix/Linux box and point snmpwalk to it and pull all available info. That, paired with the MIB file, is usually the best way to make sure which element you want. If on Windows, there are several free SNMP clients that can "snmpwalk" a device and do the equivalent.
Let me know how that goes!
You can try the OID 1.3.6.1.2.1.4.20 to get the list of IP add with corresponding interfaces via SNMP.
Actually, i had a list of IPs before, i needed just to match them with int names. I did it using 2 MIBs - 1.3.6.1.2.1.4.20.1.2.+IPaddress returns the index of interface and using this index i used 1.3.6.1.2.1.2.2.1.2.+IntfIndex (obtained in previous step). I did it for every IP address in list and works like charm.
There is also the ifxTable which has improved interface speed information for high speed ethernet ports:
http://tools.cisco.com/Support/SNMP/do/BrowseOID.do?local=en&translate=true&objectInput=ifXTable
I am using NET-SNMP (V5.6.1.1) on windows to read my MIB with snmpget & snmpwalk. When I try accessing the MIB I can only see some of the elements. I know the MIB is good since my colleague can extract the same revision of the MIB from the repository and can see all elements within the MIB. We are using the same SNMP command syntax to query the data. I have compared the MIB and snmp.conf files between his machine and mine and they are identical, so can only assume that it is due to a difference in the configuration of our respective PCs. I’ve also checked for any differences in the Environment Variables between our machines, but can see nothing obvious. Is there anything in the machine configuration that might explain why I can only see part of the MIB?
Edit: The MIB is implemented as a single bespoke executable, with the data held in a number of tables, for example:
mibTableA.parameter1
mibTableA.parameter2
mibTableA.parameter3
mibTableB.parameter4
mibTableB.parameter5
mibTableC.parameter6
mibTableC.parameter7
mibTableC.parameter8
None of these tables are dependant upon the availability of system hardware, etc. These tables can also be accesses via an RTA interface using PSQL queries, and using the RTA interface on both my machine and my colleague’s machines, I can see all the tables/parameters. Yet, for instance, accessing the MIB via SNMP I can only see the mibTableA on my machine.
First you need to identify which are the missing ones on your box. Show some examples in your question so that others can guess what can be the cause.
Second, SNMP query result is indeed machine dependent. For example, if your machine has less network adapters than your friend's, then it is reasonable some objects are missing.
I found the problem. There are some scalar fields in the MIB which define the table sizes and these had not been initialised correctly, but instead were picking up old values stored in tables in a C:\Documents and Settings\user\Application Data folder. Hence the difference in behaviour between my machine and my colleagues.
I want to implement SNMP-agent for PowerPC board using net-snmp.
Previously it was implemented using SMASH. SMASH has a parser
which could read MIB and generate C code (blank function imlementation)
How do I get started?
Try to look at mib2c tool from net-snmp. It will generate the snmp agent C code from the MIB. Then you have to only fulfill the return values to SNMP requests. Skeleton of responding to SNMP requests (get, set, get-next) are automatically done by generating.
Do you have a look to Writing a MIB module tutorial.
I took a different approach to this. In order to better integrate with my C++ ecosystem, and to obtain greater flexibility (particularly at scale), I:
Had a pre-build step parse the result of snmptranslate (that is, the MIB tree) into a bunch of C++ maps and other containers for use in code
Borrowed Net-SNMP's transport and PDU building functions
But serviced requests myself upon receipt, using my C++ maps and the data already available to my application
This made notification generation trivial (I just needed some variant types to generate varbinds, a bit of PDU construction and then left the rest to Net-SNMP's transport feature), although for requests I did then have to implement table walking myself (and GetNext/GetBulk/Set are not trivial unless you avoid all tables, or at least avoid composite-index tables).
The result is a fast, robust and scalable SNMP agent with expressive code that's easy to maintain and to extend.
You don't say you're using C++, but this does give an idea of how you can cherry-pick Net-SNMP functionality without necessarily buying into its entire ecosystem.
Do note that I have no idea how SNMPv3 would fit into this model; I cleverly left the company before it became my problem. :)
I am using some SNMP traps for monitoring of applications. Now I was told that some monitoring systems might have problems if the order of the attributes within the the traps was not the same as defined in the MIB. From the Complexity of the OIDs that could easily be used to re-order the attributes I was surprised by this, so I tried to find the relevant section of the RFC, but I could neither find something that said any ordering is allowed nor anything that said it is important. In other secondary documentation about SNMP I was not able to find anything usefull either.
So this is more a curiosity question, that could however also help in further projects using SNMP. Could anyone point me to the correct documentation as far as this problem is concerned. Or is this something that one software might handle while other software might not handle this and I should check the actual documentation for that software?
I found the relevant document.
Section 3.1.2 specifies:
The VARIABLES clause, which need not be present, defines the
ordered sequence of MIB objects which are contained within
every instance of the trap type. Each variable is placed, in
order, inside the variable-bindings field of the SNMP Trap-
PDU. Note that at the option of the agent, additional
variables may follow in the variable-bindings field.
Thanks to the person who pointed this out to me.
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'.