RE: SNMP Protocol

By network devices I mean small nework devices based on embedded Linux system, such as cable modems, eMTA, set-top boxes, smart TVs.

----- Original Message -----
From: Robson, Alan
Sent: 04/11/14 01:57 AM
To: Alex, [email protected]
Subject: RE: SNMP Protocol

The Management Information Base (MIB) will be hard coded into the program running on the network device (The SNMP agent). This SNMP agent can use any technique it likes to store its information (for example, my snmp agent stores all its information in mysql).
A file describing the MIB (generally known as MIB files) for particular systems may be available on the internet, that would be common for the major vendors like Cisco for example, many of their mib files are available for free download from cisco.com. Also, many snmp agents support standard mibs defined in the RFCs for things like interface statistics, uptime etc.
Some SNMP agents (like net-snmp) can be extended with subagents. The original agent responds to common requests like uptime, system name, IP addresses etc. and custom subagents are created to add additional information. If your network device is equivalent to a PC running net-snmp snmpd then it may be possible to add information to the MIB on the machine, either by putting configuration into snmpd.conf or by writing your own subagent. When you say network device though, it makes me think you are talking about a system that you cannot easily add your own software to.
From: Alex [mailto:[email protected]]
 *Sent:* Thursday, April 10, 2014 1:23 PM
 *To:* [email protected]
 *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:  [email protected] 
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, < [email protected] > 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)?


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