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Simple Network Management Protocol - Wikipedia, the free encyclopedia

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Simple Network Management ProtocolFrom Wikipedia, the free encyclopedia

The simple

The five-layer TCP/IP model 5. Application layer DHCP DNS FTP Gopher HTTP IMAP4 IRC NNTP XMPP MIME POP3 SIP SMTP SNMP SSH TELNET RPC RTP RTCP TLS/SSL SDP SOAP VPN PPTP L2TP GTP 4. Transport layer TCP UDP DCCP SCTP 3. Internet layer IP (IPv4 IPv6) IGMP ICMP RSVP BGP RIP OSPF ISIS IPsec ARP RARP 2. Data link layer 802.11 ATM DTM Ethernet FDDI Frame Relay GPRS EVDO HSPA HDLC PPP 1. Physical layer Ethernet physical layer ISDN Modems PLC SONET/SDH G.709 WiMAX 12/7/07

Simple Network Management Protocol - Wikipedia, the free encyclopedia

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network management protocol (SNMP) forms part of the internet protocol suite as defined by the Internet Engineering Task Force (IETF). SNMP is used by network management systems to monitor network-attached devices for conditions that warrant administrative attention. It consists of a set of standards for network management, including an Application Layer protocol, a database schema, and a set of data objects.[1]


SNMP exposes management data in the form of variables on the managed systems, which describe the system configuration. These variables can then be queried (and sometimes set) by managing applications.

Contents1 Overview and Basic Concepts 2 Management Information Base (MIBs) 2.1 Abstract Syntax Notation One (ASN.1) 3 SNMP Basic Components 3.1 SNMP Architecture 3.1.1 Master Agent 3.1.2 Subagent 3.1.3 Management Station 3.2 SNMP Protocol 3.2.1 SNMPv1 and SMI-Specific Data Types Simple data types Application-wide data types 3.2.2 SNMPv1 MIB Tables 3.2.3 SNMPv2 and Structure of Management Information 12/7/07

Simple Network Management Protocol - Wikipedia, the free encyclopedia

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3.2.4 SNMPv2 SMI Information Modules 3.2.5 SNMPv3 3.3 Development and Usage 3.3.1 Version 1 3.3.2 Version 2 3.3.3 SNMPv1 & SNMPv2c Interoperability 3.3.4 Proxy Agents 3.3.5 Bilingual Network-Management System 3.3.6 Version 3 3.4 Usage Examples 3.5 Other SNMP Topics 3.5.1 Autodiscovery 3.5.2 Negative Impact 3.5.3 Index Shifting 3.5.4 Security Implications 4 RFCS and Other References 4.1 RFCs 4.2 See also 4.3 External links 4.3.1 Implementations 5 References

Overview and Basic ConceptsIn typical SNMP usage, there are generally a number of systems to be managed, and one or more systems managing them. A software component called an agent (see below) runs on each managed system and reports information via SNMP to the managing systems. Essentially, SNMP agents expose management data on the 12/7/07

Simple Network Management Protocol - Wikipedia, the free encyclopedia

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managed systems as variables (such as "free memory", "system name", "number of running processes", "default route"). The managing system can retrieve the information through the GET, GETNEXT and GETBULK protocol operations or the agent will send data without being asked using TRAP or INFORM protocol operations. Management systems can also send configuration updates or controlling requests through the SET protocol operation to actively manage a system. Configuration and control operations are used only when changes are needed to the network infrastructure and the monitoring operations are frequently performed on a regular basis. The variables accessible via SNMP are organized in hierarchies. These hierarchies, and other metadata, are described by Management Information Bases (MIBs).

Management Information Base (MIBs)The SNMP's extensible design is achieved with management information bases (MIBs), which specify the management data of a device subsystem, using a hierarchical namespace containing object identifiers, implemented via ASN.1. The MIB hierarchy can be depicted as a tree with a nameless root, the levels of which are assigned by different organizations. The top-level MIB object IDs belong to different standards organizations, while lower-level object IDs are allocated by associated organizations. This model permits management across all layers of the OSI reference model, extending into applications such as databases, email, and the Java EE reference model, as MIBs can be defined 12/7/07

Simple Network Management Protocol - Wikipedia, the free encyclopedia

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for all such area-specific information and operations. A MIB is a collection of information that is organized hierarchically. MIBs are accessed using a network-management protocol such as SNMP. They comprise managed objects and are identified by object identifiers. A managed object (sometimes called a MIB object, an object, or a MIB) is one of any number of specific characteristics of a managed device. Managed objects comprise one or more object instances, which are essentially variables. Two types of managed objects exist: 1. Scalar objects define a single object instance. 2. Tabular objects define multiple related object instances that are grouped in MIB tables. An example of a managed object is atInput, which is a scalar object that contains a single object instance, the integer value that indicates the total number of input AppleTalk packets on a router interface. An object identifier (or object ID or OID) uniquely identifies a managed object in the MIB hierarchy.

Abstract Syntax Notation One (ASN.1)In telecommunications and computer networking, Abstract Syntax Notation One (ASN.1) is a standard and flexible notation that describes data structures for representing, encoding, 12/7/07

Simple Network Management Protocol - Wikipedia, the free encyclopedia

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transmitting, and decoding data. It provides a set of formal rules for describing the structure of objects that are independent of machine-specific encoding techniques and is a precise, formal notation that removes ambiguities. ASN.1 is a joint ISO and ITU-T standard, originally defined in 1984 as part of CCITT X.409:1984. ASN.1 moved to its own standard, X.208, in 1988 due to wide applicability. The substantially revised 1995 version is covered by the X.680 series. An adapted subset of ASN.1, Structure of Management Information (SMI), is specified in SNMP to define sets of related MIB objects; these sets are termed MIB modules.

SNMP Basic ComponentsA SNMP-managed network consists of three key components: 1. Managed devices 2. Agents 3. Network-management systems (NMSs) A managed device is a network node that contains a SNMP agent and that resides on a managed network. Managed devices collect and store management information and make this information available to NMSs using SNMP. Managed devices, sometimes called network elements, can be routers and access servers, switches and bridges, hubs, computer hosts, or printers. An agent is a network-management software module that resides 12/7/07

Simple Network Management Protocol - Wikipedia, the free encyclopedia

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in a managed device. An agent has local knowledge of management information and translates that information into a form compatible with SNMP. An NMS executes applications that monitor and control managed devices. NMSs provide the bulk of the processing and memory resources required for network management. One or more NMSs may exist on any managed network.

SNMP ArchitectureThe SNMP framework consists of master agents, subagents and management stations.

Master AgentA master agent is a piece of software running on a SNMPcapable network component, for example a router that responds to SNMP requests from the management station. Thus it acts as a server in client-server architecture terminology or as a daemon in operating system terminology. A master agent relies on subagents to provide information about the management of specific functionality. Master agents can also be referred to as managed objects.

SubagentA subagent is a piece of software running on a SNMP-capable network component that implements the information and 12/7/07

Simple Network Management Protocol - Wikipedia, the free encyclopedia

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management functionality defined by a specific MIB of a specific subsystem.: for example the ethernet link layer. Some capabilities of the subagent are: Gathering information from managed objects Configuring parameters of the managed objects Responding to managers' requests Generating alarms or traps

Management StationThe manager or management station is the final component in the SNMP architecture. It functions as the equivalent of a client in the client-server architecture. It issues requests for management operations on behalf of a administrator or application and receives traps from agents as well.

SNMP ProtocolSNMPv1 and SMI-Specific Data TypesThe SNMPv1 SMI specifies the use of a number of SMI-specific data types, which are divided into two categories: 1. Simple data types 2. Application-wide data types Simple data types Three simple data types are defined in the SNMPv1 SMI, all of which are unique values