![Simple Network Management Protocol (SNMP) is an "Internet-standard protocol for managing
devices on IP networks". Devices that typically support SNMP include routers, switches, servers,
workstations, printers, modem racks, and more.[1] It is used mostly in network management
systems to monitor network-attached devices for conditions that warrant administrative attention.
SNMP is a component of the Internet Protocol Suite as defined by the Internet Engineering Task
Force (IETF). It consists of a set of standards for network management, including an application
layer protocol, a database schema, and a set of data objects.[2]
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.
Contents
[hide]
1 Overview and basic concepts
2 Management information base (MIB)
3 Protocol details
o 3.1 GetRequest
o 3.2 SetRequest
o 3.3 GetNextRequest
o 3.4 GetBulkRequest
o 3.5 Response
o 3.6 Trap
o 3.7 InformRequest
4 Development and usage
o 4.1 Version 1
o 4.2 Version 2
o 4.3 SNMPv1 & SNMPv2c interoperability
4.3.1 Proxy agents
4.3.2 Bilingual network-management system
o 4.4 Version 3
5 Implementation issues
6 Resource indexing
7 Security implications
o 7.1 Autodiscovery
8 RFC references
9 See also](https://image.slidesharecdn.com/simplenetworkmanagementprotocol-130316142238-phpapp02/85/Simple-network-management-protocol-1-320.jpg)
![10 References
11 External links
[edit]Overview and basic concepts
Principle of SNMP Communication
In typical SNMP uses, one or more administrative computers, called managers, have the task of
monitoring or managing a group of hosts or devices on a computer network. Each managed
system executes, at all times, a software component called an agent which reports information
via SNMP to the manager.
Essentially, SNMP agents expose management data on the managed systems as variables. The
protocol also permits active management tasks, such as modifying and applying a new
configuration through remote modification of these variables. The variables accessible via SNMP
are organized in hierarchies. These hierarchies, and other metadata (such as type and
description of the variable), are described by Management Information Bases(MIBs).
An SNMP-managed network consists of three key components:
• Managed device
• Agent — software which runs on managed devices
• Network management system (NMS) — software which runs on the manager
A managed device is a network node that implements an SNMP interface that allows
unidirectional (read-only) or bidirectional access to node-specific information. Managed devices
exchange node-specific information with the NMSs. Sometimes called network elements, the
managed devices can be any type of device, including, but not limited to, routers, access
servers, switches,bridges, hubs, IP telephones, IP video cameras, computer hosts, and printers.
An agent is a network-management software module that resides on a managed device. An
agent has local knowledge of management information and translates that information to or from
an SNMP specific form.
A network management system (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.
[edit]Management information base (MIB)
Main article: Management information base](https://image.slidesharecdn.com/simplenetworkmanagementprotocol-130316142238-phpapp02/85/Simple-network-management-protocol-2-320.jpg)
![SNMP itself does not define which information (which variables) a managed system should offer.
Rather, SNMP uses an extensible design, where the available information is defined
bymanagement information bases (MIBs). MIBs describe the structure of the management data
of a device subsystem; they use a hierarchical namespace containing object identifiers (OID).
Each OID identifies a variable that can be read or set via SNMP. MIBs use the notation defined
by ASN.1.
[edit]Protocol details
SNMP operates in the Application Layer of the Internet Protocol Suite (Layer 7 of the OSI model).
The SNMP agent receives requests on UDP port 161. The manager may send requests from any
available source port to port 161 in the agent. The agent response will be sent back to the source
port on the manager. The manager receives notifications (Traps and InformRequests) on port
162. The agent may generate notifications from any available port. When used with Transport
Layer Security or Datagram Transport Layer Security requests are received on port 10161 and
traps are sent to port 10162.[3]
SNMPv1 specifies five core protocol data units (PDUs). Two other
PDUs, GetBulkRequest and InformRequest were added in SNMPv2 and carried over to SNMPv3.
All SNMP PDUs are constructed as follows:](https://image.slidesharecdn.com/simplenetworkmanagementprotocol-130316142238-phpapp02/85/Simple-network-management-protocol-3-320.jpg)
Simple network management protocol
- 1. Simple Network Management Protocol (SNMP) is an "Internet-standard protocol for managing devices on IP networks". Devices that typically support SNMP include routers, switches, servers, workstations, printers, modem racks, and more.[1] It is used mostly in network management systems to monitor network-attached devices for conditions that warrant administrative attention. SNMP is a component of the Internet Protocol Suite as defined by the Internet Engineering Task Force (IETF). It consists of a set of standards for network management, including an application layer protocol, a database schema, and a set of data objects.[2] 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. Contents [hide] 1 Overview and basic concepts 2 Management information base (MIB) 3 Protocol details o 3.1 GetRequest o 3.2 SetRequest o 3.3 GetNextRequest o 3.4 GetBulkRequest o 3.5 Response o 3.6 Trap o 3.7 InformRequest 4 Development and usage o 4.1 Version 1 o 4.2 Version 2 o 4.3 SNMPv1 & SNMPv2c interoperability 4.3.1 Proxy agents 4.3.2 Bilingual network-management system o 4.4 Version 3 5 Implementation issues 6 Resource indexing 7 Security implications o 7.1 Autodiscovery 8 RFC references 9 See also
- 2. 10 References 11 External links [edit]Overview and basic concepts Principle of SNMP Communication In typical SNMP uses, one or more administrative computers, called managers, have the task of monitoring or managing a group of hosts or devices on a computer network. Each managed system executes, at all times, a software component called an agent which reports information via SNMP to the manager. Essentially, SNMP agents expose management data on the managed systems as variables. The protocol also permits active management tasks, such as modifying and applying a new configuration through remote modification of these variables. The variables accessible via SNMP are organized in hierarchies. These hierarchies, and other metadata (such as type and description of the variable), are described by Management Information Bases(MIBs). An SNMP-managed network consists of three key components: • Managed device • Agent — software which runs on managed devices • Network management system (NMS) — software which runs on the manager A managed device is a network node that implements an SNMP interface that allows unidirectional (read-only) or bidirectional access to node-specific information. Managed devices exchange node-specific information with the NMSs. Sometimes called network elements, the managed devices can be any type of device, including, but not limited to, routers, access servers, switches,bridges, hubs, IP telephones, IP video cameras, computer hosts, and printers. An agent is a network-management software module that resides on a managed device. An agent has local knowledge of management information and translates that information to or from an SNMP specific form. A network management system (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. [edit]Management information base (MIB) Main article: Management information base
- 3. SNMP itself does not define which information (which variables) a managed system should offer. Rather, SNMP uses an extensible design, where the available information is defined bymanagement information bases (MIBs). MIBs describe the structure of the management data of a device subsystem; they use a hierarchical namespace containing object identifiers (OID). Each OID identifies a variable that can be read or set via SNMP. MIBs use the notation defined by ASN.1. [edit]Protocol details SNMP operates in the Application Layer of the Internet Protocol Suite (Layer 7 of the OSI model). The SNMP agent receives requests on UDP port 161. The manager may send requests from any available source port to port 161 in the agent. The agent response will be sent back to the source port on the manager. The manager receives notifications (Traps and InformRequests) on port 162. The agent may generate notifications from any available port. When used with Transport Layer Security or Datagram Transport Layer Security requests are received on port 10161 and traps are sent to port 10162.[3] SNMPv1 specifies five core protocol data units (PDUs). Two other PDUs, GetBulkRequest and InformRequest were added in SNMPv2 and carried over to SNMPv3. All SNMP PDUs are constructed as follows: