| 5.4 |  | SNMP |
| 5.4.1 |  | SNMP introduction |

| Another technique that the administrator can use to manage and monitor the network is to employ the Simple Network Management Protocol (SNMP). SNMP is an application-layer protocol that facilitates the exchange of management information between network devices. It is part of the TCP/IP protocol suite. SNMP enables network administrators to manage network performance, find and solve network problems, and plan for network growth. SNMP can be used to manage Cisco routers, switches, wireless access points, firewalls, printers, servers and other SNMP capable devices .

There are three versions of SNMP:

Version | RFC | Adopted by IETF
SNMPv1 | 1157 - 1162 | 1989
SNMPv2 | 1901 - 1908 | 1993
SNMPv3 | 3410 - 3418 | 2002

SNMPv1 and SNMPv2 have features in common, but SNMPv2 offers enhancements, such as additional protocol operations. SNMPv3 adds administration and security features. This section provides descriptions of the SNMPv3 protocol operations. Cisco recommends disabling SNMP if not in use or use version 3.

Figure illustrates a basic network managed by SNMP.

SNMP basic components

An 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 an SNMP agent and 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, switches, wireless access points, firewalls, printers, servers and other SNMP capable devices.

An agent is a network management software module that resides 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 must exist on any managed network. SNMP management applications, such as CiscoWorks2000, communicate with agents to get statistics and alerts from the managed devices.

SNMP basic commands

Managed devices are monitored and controlled using basic SNMP commands, as shown in Figure :

- The

read command is used by an NMS to monitor managed devices. The NMS examines different variables that are maintained by managed devices.
- The
write command is used by an NMS to control managed devices. The NMS changes the values of variables stored within managed devices.
- Managed devices to asynchronously report events to the NMS use the
trap command. When certain types of events occur, a managed device sends a trap to the NMS.
- Traversal operations are used by the NMS to determine which variables a managed device supports and to sequentially gather information in variable tables, such as a routing table.

The basic SNMP process is shown in Figure .