Juniper Networks J-Series manual Management Information Base, Snmp Communities

J-series™ Services Router Administration Guide

Communication between the agent and the manager occurs in one of the following forms:

■Get, GetBulk, and GetNext requests—The manager requests information from the agent, and the agent returns the information in a Get response message.

■Set requests—The manager changes the value of a MIB object controlled by the agent, and the agent indicates status in a Set response message.

■Traps notification—The agent sends traps to notify the manager of significant events that occur on the network device.

Management Information Base

Agents store information in a hierarchical database called the Structure of Management Information (SMI). The SMI resembles a file system. Information is stored in individual files that are hierarchically arranged in the database. The individual files that store the information are known as Management Information Bases (MIBs). Each MIB contains nodes of information that are stored in a tree structure. Information branches down from a root node to individual leaves in the tree, and the individual leaves comprise the information that is queried by managers for a given MIB. The nodes of information are identified by an object ID (OID). The OID is a dotted integer identifier (1.3.6.1.2.1.2, for instance) or a subtree name (such as interfaces) that corresponds to an indivisible piece of information in the MIB.

MIBs are either standard or enterprise-specific. Standard MIBs are created by the Internet Engineering Task Force (IETF) and documented in various RFCs. Depending on the vendor, many standard MIBs are delivered with the NMS software. You can also download the standard MIBs from the IETF Web site, http://www.ietf.org, and compile them into your NMS, if necessary.

For a list of standard and enterprise-specific supported MIBS, see the JUNOS Network Management Configuration Guide.

Enterprise-specific MIBs are developed and supported by a specific equipment manufacturer. If your network contains devices that have enterprise-specific MIBs, you must obtain them from the manufacturer and compile them into your network management software.

To download enterprise MIBs for a Services Router, go to

http://www.juniper.net/techpubs/software/index_mibs.html.

SNMP Communities

You can grant access to only specific SNMP managers for particular SNMP agents by creating SNMP communities. The community is assigned a name that is unique on the host. All SNMP requests that are sent to the agent must be configured with the same community name. When multiple agents are configured on a particular host, the community name process ensures that SNMP requests are sorted to only those agents configured to handle the requests.

Additionally, communities allow you to specify one or more addresses or address prefixes to which you want to either allow or deny access. By specifying a list of

48■ SNMP Architecture