Ok – let’s try this another way – rather than think of a MIB as a database in
the traditional sense of a repository where information is placed, think of it
more as a specification of how data is stored or ‘mapped’. In this way, a SNMP
agent (software – typically a daemon or background process which runs on a host
such as a server, router, etc. ) is coded to the MIB specifications.
In a similar way, a management station may load a MIB in order to understand
what the returned information ‘means’ in human-readable form. Let’s take an
example from RFC1155-SMI &RFC1213 (MIB II):
RFC1155 defines the root of the tree:
internet OBJECT IDENTIFIER ::= { iso org(3) dod(6) 1 }
directory OBJECT IDENTIFIER ::= { internet 1 }
mgmt OBJECT IDENTIFIER ::= { internet 2 }
experimental OBJECT IDENTIFIER ::= { internet 3 }
private OBJECT IDENTIFIER ::= { internet 4 }
enterprises OBJECT IDENTIFIER ::= { private 1 }
mib-2 OBJECT IDENTIFIER ::= { mgmt 1 }
system OBJECT IDENTIFIER ::= { mib-2 1 }A
RFC1213 begins to add branches after importing RFC1155
sysDescr OBJECT-TYPE
SYNTAX DisplayString (SIZE (0..255))
ACCESS read-only
STATUS mandatory
DESCRIPTION
"A textual description of the entity. This value
should include the full name and version
identification of the system's hardware type,
software operating-system, and networking
software. It is mandatory that this only contain
printable ASCII characters."
::= { system 1 }
We can express the object identifier (OID) sysDescr as: 1.3.6.1.2.1.1.1 OR as
RFC1213-MIB::sysDescr
In other words, the MIB is used to define the structure of the information.
As a SNMP agent is being built, it makes use of the MIB structure to define
that when a management station requests 1.3.6.1.2.1.1.1.0, the software is
supposed to return a description of the software running on the host. Without
having the MIB loaded in a management station, it would be perfectly possible
to retrieve the information, but it’s a whole lot easier to understand this:
RFC1213-MIB::sysDescr.0 = STRING: "Cisco Internetwork Operating System Software”
RFC1213-MIB::sysObjectID.0 = OID: CISCO-PRODUCTS-MIB::ciscoWSC6509neba
RFC1213-MIB::sysContact.0 = "Me"
RFC1213-MIB::sysName.0 = STRING: “myrouter"
RFC1213-MIB::sysLocation.0 = "Under my desk"
RFC1213-MIB::sysServices.0 = INTEGER: 78
SNMPv2-MIB::sysORLastChange.0 = Timeticks: (0) 0:00:00.00
Than:
1.3.6.1.2.1.1.1 = STRING: "Cisco Internetwork Operating System Software”
1.3.6.1.2.1.1.2=1.3.6.1.4.1.9.5.1.3.1.1.2.291
1.3.6.1.2.1.1.3= "Me"
1.3.6.1.2.1.1.4= STRING: “myrouter"
1.3.6.1.2.1.1.5= "Under my desk"
1.3.6.1.2.1.1.6= INTEGER: 78
1.3.6.1.2.1.1.7= Timeticks: (0) 0:00:00.00
Hope this is helpful
From: Alex [mailto:laguna...@mail.com]
Sent: Thursday, April 10, 2014 4:23 PM
To: net-snmp-users@lists.sourceforge.net
Subject: Re: SNMP Protocol
Hi,
Thank you for input.
I don't understand. I've read specification RFC 2741 and RFC 1157, not full
though, just important moments. My understanding is that SNMP is protocol, SNMP
agent is plain daemon that run on the background, and MIB files is a sort of
centralized database, where agent sends a request. Therefore MIB database must
be installed somewhere. If MIB files is not installed, where SNMP agent will
take information about OID values?
Well, suppose it depends on application and network device. Where the MIB
files resides on cable modem or set-top box, for example? Is it hard-coded into
their program code or they are located on a management station? If its
hard-coded inside program code, then to add a new MIB file requires replacement
of the entire software, if its on management station, then we just need add new
MIB to database which is more easy?
Thanks
----- Original Message -----
From: Joel Hansell
Sent: 04/10/14 06:37 PM
To: laguna...@mail.com<mailto:laguna...@mail.com>
Subject: Re: SNMP Protocol
Dear Anonymous,
In principle, the MIB files don't have to be installed anywhere. They are only
a specification. The describe which objects are available on the agent, and
which notifications the agent may send.
Some SNMP managers let the user "load" MIB files, in order to better present
the data fetched from the agents. But this is not mandatory.
Some SNMP agents let the user "load" MIB files, to alter structure of the data
which is published, but this is more unusual. Many SNMP agents in industrial
use have the MIB structure hard-coded into their program code.
I'm sure such an answer will lead to more questions, please go ahead. :-)
Regards,
Joel Hansell
On Thu, Apr 10, 2014 at 4:25 PM,
<laguna...@mail.com<mailto:laguna...@mail.com>> wrote:
question about SNMP Protocol: where is installed MIB files (vendor-specific):
on the Network management station (NMS) or on the network devices (network
node)?
------------------------------------------------------------------------------
Put Bad Developers to Shame
Dominate Development with Jenkins Continuous Integration
Continuously Automate Build, Test & Deployment
Start a new project now. Try Jenkins in the cloud.
http://p.sf.net/sfu/13600_Cloudbees
_______________________________________________
Net-snmp-users mailing list
Net-snmp-users@lists.sourceforge.net<mailto:Net-snmp-users@lists.sourceforge.net>
Please see the following page to unsubscribe or change other options:
https://lists.sourceforge.net/lists/listinfo/net-snmp-users
T. Rowe Price (including T. Rowe Price Group, Inc. and its affiliates) and its
associates do not provide legal or tax advice. Any tax-related discussion
contained in this e-mail, including any attachments, is not intended or written
to be used, and cannot be used, for the purpose of (i) avoiding any tax
penalties or (ii) promoting, marketing, or recommending to any other party any
transaction or matter addressed herein. Please consult your independent legal
counsel and/or professional tax advisor regarding any legal or tax issues
raised in this e-mail.
The contents of this e-mail and any attachments are intended solely for the use
of the named addressee(s) and may contain confidential and/or privileged
information. Any unauthorized use, copying, disclosure, or distribution of the
contents of this e-mail is strictly prohibited by the sender and may be
unlawful. If you are not the intended recipient, please notify the sender
immediately and delete this e-mail.
------------------------------------------------------------------------------
Put Bad Developers to Shame
Dominate Development with Jenkins Continuous Integration
Continuously Automate Build, Test & Deployment
Start a new project now. Try Jenkins in the cloud.
http://p.sf.net/sfu/13600_Cloudbees
_______________________________________________
Net-snmp-users mailing list
Net-snmp-users@lists.sourceforge.net
Please see the following page to unsubscribe or change other options:
https://lists.sourceforge.net/lists/listinfo/net-snmp-users
