[ Contents ] [ Index
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Simple Network Management Protocol (SNMP) is one of the most widely
used protocols for network management. It does what its name says: it
manages network devices in a relatively simple manner. SNMP is a simple,
unacknowledged, connectionless protocol. SNMP was originally developed to work under the umbrella of the Internet
suite of protocols, primarily in TCP/IP (Transmission Control Protocol/Internet
Protocol) transport protocols. Since then, SNMP has been implemented to
work over other common transport protocols, such as Novells IPX/SPX
(Internet Packet Exchange/Sequenced Packet Exchange). SNMP Trap Messages Agents use SNMP to send information to enterprise management systems. Once a server is configured to send traps, SANscape event information flows to that system. SANscapes trap messages contain the following information:
The information that is displayed and its format are dependent on the SNMP management console you are using. The file RST_OID.MIB must be loaded into the enterprise management console for traps to be received. On a Solaris, Linux, and HP-UX OS, this file is located in /opt/dothill/ssagent. On an IBM AIX OS, this file is located in /usr/dothill/ssagent. On Microsoft Windows, this file is located in \Program Files\Dot HIll\ssagent. Agents and Managers The SNMP software model consists of agents
and managers. An agent is the software that enables variables in the managed
device to be monitored. The agent software is either embedded in the device
that is managed or running on a computer to which the device is connected. Management Information Base (MIB) On a network, each device instrumented by SNMP agents has one or more variables or objects associated with it. An example of a typical variable might be one that keeps track of the name of the device. These variables or objects are described in a text file called Management Information Base (MIB). A MIB is a precise textual definition of variables being managed. The procedures for defining a MIB have been established by the Internet Engineering Task Force (IETF) of the International Standards Organization (ISO). SNMP Objects Some variables for network management are
common to all LAN network devices. Many of these variables have been standardized
and are referred to as MIB-II variables and MIB-II extensions. The IETF
has also defined the procedures for MIBs that are not in a standard MIB-II
category. These variables are listed in private enterprise MIBs. SNMP Request Types The SNMP operations that support accessing MIB data are Get, GetNext, and Set. Get retrieves a scalar value from a table entry field value, given an index value. GetNext is used to traverse the instances of table entries, with each command returning the next sequential value in the column (or field) of interest. The Set operation is used to create or change the value of a MIB variable. SNMP Security Setting values raises the issue of security. SNMP V1 (version 1) has a simple security scheme. Each protocol data unit (PDU) contains a community string, which is like a combination of user name and password. Each agent can be configured for a particular community string. An agent does not respond to a request sent to it except when the community string in the request PDU matches the community string in its own configuration. |