Shulou(Shulou.com)06/01 Report--

Simple Network Management Protocol (SNMP,Simple Network Management Protocol) forms part of the Internet protocol suite defined by the Internet Engineering working Group (IETF,Internet Engineering Task Force). The protocol can support the network management system to monitor whether the devices connected to the network have any management concerns. It consists of a set of network management standards, including an application layer protocol (application layer protocol), a database model (database schema), and a set of data objects.

SNMP is a very important protocol. All kinds of parameters are written into the MIB library on the monitored equipment, and the administrator can read these parameters and even modify them through various network management software. These actions can be realized in the graphical interface through the network management software. The interaction between the network management software and the agent of the monitored device is through the SNMP protocol. So let's take a look at some details of SNMP.

SNMP component

The use of SNMP for network management requires the following important parts: management base stations, network management tools, management agents, management information bases and managed devices.

The management base station is usually an independent device, which is used as the user interface for network managers to manage the network. The base station must be equipped with management software, a user interface that the administrator can use and a database to obtain information from MIB. At the same time, it should have the ability to issue management commands to the base station for network management.

The network management tools are the management software installed on the base station.

L management agent is a kind of software that runs SNMP server programs of managed devices (such as hosts, bridges, routers and hubs). It can receive information from management base stations, and their status can also be monitored by management base stations. The management agent performs the corresponding operation in response to the request of the base station and can also send information to the base station without a request.

LMIB,Management Information Base: a management information base that stores various parameters on the monitored device. MIB contains parameters that can be queried and modified by all agent processes. The current version is MIB- Ⅱ. When it comes to MIB, it is necessary to introduce the very important concept of object representation (OID).

OID: is a point (".") A segmented sequence of integers that form a tree structure, similar to the DNS or Linux file system. OID starts at the top of the tree, and there is no identification at the top, represented by root. OID is not randomly assigned, it is managed and assigned by an authoritative body. (see OID structure diagram below)

L managed devices are managed routers, switches, servers, printers, hosts, and so on.

The relationship between several components of SNMP can be clearly reflected in the following figure (SNMP component diagram)

SNMP interaction process

There are five types of messages that interact between SNMP management processes and agent processes:

(1) get-request operation: one or more parameter values are extracted from the agent process (udp 161).

(2) get-next-request operation: the next parameter value of one or more parameters is extracted from the agent process (udp 161).

(3) set-request operation: set one or more parameter values of the proxy process. The open port of the proxy process is udp 161.

(4) get-response operation: one or more parameter values issued by the agent process respond to the request submitted by the management process and return one or more parameter values from the UDP port 161of the agent process.

(5) trap operation: a message sent by the agent process to notify the management process (udp 162) that something has happened.

The first three operations are issued by the management process to the agent process, and the last two are sent by the agent process to the management process.

Then use the following figure to see the process of interaction.

Basically, SNMP agents present management data as variables. The management system retrieves information through GET,GETNEXT operations, or agents use TRAP to transmit data without being questioned. The management system can also send requests for configuration updates or control, and achieve the purpose of actively managing the system through SET protocol instructions. Configuration and control instructions are used only when the basic structure of the network needs to be changed, while monitoring instructions are usually routine.

III. Three versions of SNMP

First edition

Data types of SNMP first Edition and SMI specifications SNMP first Edition SMI specifies the data types of many SMI specifications, which are divided into two main categories:

Simple data type

Universal application data type

SNMPv1 uses group name for message authentication

The second edition

The second edition of SNMP and the second edition of SNMP SMI are described in RFC 2578, which adds and enhances the SMI specification data types of the first edition of SNMP, such as bit strings (bit strings), network addresses (network addresses), and counters (counters).

The SNMP protocol operates at the application layer (layer 7) of the OSI model, specifying five core PDU in the first edition:

GET REQUEST

GET NEXT REQUEST

GET RESPONSE

SET REQUEST

TRAP

Other PDU is added in the second edition of SNMP, including:

GETBULK REQUEST

INFORM

SNMP second edition SMI information module SNMP second edition SMI also specifies an information module to specify the definition of a group of associations. There are three SMI information modules: MIB module, response status, and capability status.

The third edition

SNMP version 3 SNMP version 3, defined by RFC 3411-RFC 3418, mainly adds SNMP enhancements in terms of security and remote configuration.

The third edition of SNMP provides important security *:

Information integrity: to ensure that the packet has not been tampered with in transmission.

Certification: the inspection information comes from the correct source.

Packet encryption: avoid snooping by unauthorized sources.

SNMPv3 defines a user-based security model, which uses a shared key for message authentication.

Lab: using What's up Gold v8.01 to monitor the network

Experimental description: there are two network segments 192.168.1.0 and 192.168.2.0, in which the network management host is located in the 192.168.1.0 network segment, the ip address is 192.168.1.10, and the gateway of this network segment is 192.168.1.254 There are three network devices in the 192.168.2.0 network segment, of which the management address of the switch is 192.168.2.253 and the address of the webrel server is 192.168.2.20, and there is also a personal computer at 192.168.2.10

Experimental purpose: to monitor the network devices in these two networks by using What's up Gold v8.01 on the network management host

Experimental environment: network management host OS:Windows XP

Router: Quidway 2600 Series

Switch: Quidway S2000 Series

The web-server OS:Redhat Enterprise Linux AS v5.4 web service is provided by the

PC OS:Windows 2003

Lab Topology:

The steps of the experiment:

1. Configure PC

First put the system disk into the optical drive

Open start-Control Panel-add or remove programs and select add / remove Windows components (A)

Right-click "my computer"-"Management"

2. Configure web-server (here I omit the process of building a web server)

[root@server1 ~] # yum install / mnt/cdrom/Server/net-snmp-5.3.2.2-7.el5.i386.rpm-y or install it with rpm, follow the prompts to install the dependent software package

[root@server1 ~] # service snmpd start enable snmp service

[root@server1 ~] # chkconfig snmpd on sets the snmp service to boot self-startup

3. Configure the router

[Router] int e0

[Router-Ethernet0] ip add 192.168.1.254 24

[Router-Ethernet0] int e1

[Router-Ethernet1] ip add 192.168.2.254 24

[Router-Ethernet1] quit

[Router] snmp-agent / enable SNMP proxy function

[Router] snmp commu read public / set read-only community name as public

[Router] snmp commu write private / set writable community name as private

[Router] snmp sys cont Dom / set up contact

[Router] snmp sys loca jifang-1 / description contact location

[Router] snmp sys ver all / indicates that the acceptable version of snmp is all

[Router] snmp tra en / enable trap function

[Router] snmp trap source e0 / indicates the source port used by the report

[Router] snmp tra en stan linkup linkdownwarmstart coldstart / setting what conditions are reported to the network management workstation

[Router] snmp target trap add 192.168.1.10 port 162 secu public / indicates the address, port and community name of the network management workstation

4. Configure the switch

[Quidway] int Vlan-interface 1

[Quidway-Vlan-interface1] ip address192.168.2.253 24

[Quidway-Vlan-interface1] quit

[Quidway] ip route-static 0.0.0.00.0.0.0 192.168.2.254

[Quidway] snmp-agent

[Quidway] snmp-agent community read public

[Quidway] snmp-agent community write private

[Quidway] snmp-agent sys-info contact Dom

[Quidway] snmp-agent sys-info locationjifang-1

[Quidway] snmp-agent sys-info version all

[Quidway] snmp-agent trap enable

[Quidway] snmp-agent trap enable standardlinkup linkdown warmstart coldstart

[Quidway] snmp-agenttarget-host trap address udp-domain 192.168.1.10 udp-port 162 paramssecurityname public

5. Configure the network management workstation

Unzip the installation package What's_up_Gold_v8.01.rar and enter the directory formed after the decompression

In this way, the purpose of real-time monitoring of the whole network is achieved. Note: the group names set in the experiment are public and private respectively, these two values are only used in the experimental environment, and the appropriate group name should be set in the real environment.

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