Cisco SRST User Guide - Page 41

Chapter 1 Cisco SRST SNMP MIB Support SNMP Overview SNMP Overview The following sections provide an overview of the SNMP. Network Management Overview Network management takes place between two major types of systems: those in control (called managing systems) and those observed and controlled (called managed systems). The most common managing system is called a network management system (NMS). Managed systems can include hosts, servers, or network components such as routers or intelligent repeaters. To promote interoperability, the cooperating systems must adhere to a common framework and a common language, called a protocol. In the Internet network management framework, that protocol is the Simple Network Management Protocol (SNMP). SNMP is an application-layer protocol designed to facilitate the exchange of network management information between network devices. The SNMP system consists of three parts: • SNMP manager • SNMP agent • MIB The Internet network management framework is based on the idea of a managing the system interfacing to a managed system. The managing system (called a manager) runs a network management application (called an agent). The managed system runs an agent that answers status requests from the manager. The manager and the managed system exchange information using SNMP. The information exchanged between the manager and the managed system is about the Management Information Base (MIB), which defines all the information that can be seen or changed by the manager. The MIB may be either standard or proprietary, and a similar concept of the MIB must be shared by both the manager and the agent. SNMP and its MIBs are defined in a combination of system-specific language and Abstract Syntax Notation 1 (ASN.1) Although ASN.1 is a rich definition language, SNMP uses only a subset of ASN.1, which is defined in the SNMP Structure of Management Information (SMI). For transmission, SNMP is encoded according to the ASN.1 basic encoding rules (BER). SNMP may be carried over a wide choice of transport protocols. The most common combination is the User Datagram Protocol over the Internet Protocol, UDP/IP. Other possibilities include AppleTalk, Netware, and Ethernet. SNMP has facilities for identifying the requester and the operational context in which a request is to be performed by the agent, such as read-only or read-write, a MIB subset for a particular group of users, or a subset that may be elsewhere or obtained through other mechanisms (proxy). These are the facilities concerned with security. SNMP has a small number of MIB management operations it can perform for observation and control of MIB information, comprising various ways of reading (get operations), and one way of modifying (set operations). The following topics are included as part of the network management overview: • MIB Overview, page 1-28 • SNMP, page 1-29 • Internet MIB Hierarchy, page 1-30 • SNMP MIB, page 1-31 OL-7959-01 Cisco SRST SNMP MIB Release 3.4 Guide 1-27