An Introduction to SNMP - N-able Technologies

ContentsAbout this Guide 3What is SNMP? 4SNMP Actions 4How is SNMP Structured? 4How Does N-central use SNMP? 6N-central and the GET command 6N-central and Syslog Messages 6N-central SDK 7Setting Up SNMP on a Windows Device 8

N-central 7.2 An Introduction to SNMPWhat is SNMP?SNMP (Simple Network Management Protocol) is a network protocol that allows one device to queryanother device for information, change information on a device, or for one device to send a message toanother device.SNMP ActionsSNMP has three actions: GET, SET and TRAP. Their descriptions and examples are given in the table,below.Action Description ExampleGET commandSET commandTRAP messageUsed to 'get' data from a deviceUsed to 'set' or change data on adeviceAn unsolicited message sent outby a device when a set of criteriahas been metWhen one device asks another device for information, such as"tell me the status of your NIC card".When an administrator changes the value of an SNMP property ofa device , such as "change the value of your Location fields toDownstairs Lab".When a firewall detects a Denial of Service attack—it will send outan SNMP TRAP message (also referred to as a syslog message) toa specified IP address.How is SNMP Structured?SNMP data is arranged in a folder structure. In the example diagram, in order to get the serial numberof a Cisco switch, you need to navigate first to the Cisco folder, and then to the Switches folder to getthe Serial Number.SNMP Folder Structure- 4 -

N-central 7.2 An Introduction to SNMPHow Does N-central use SNMP?N-central uses SNMP in two ways:• it queries devices for information using the GET command• it receives syslog messagesThe SNMP GET command is used as part of network discovery jobs, and as part of many of N-central’smonitoring services.N-central and the GET commandN-central uses the GET command to query devices for information. This information can be divided intotwo categories:• Asset data, such as the serial number of a device, or the model and manufacturer of a device• Monitoring data, such as the status of a physical drive or RAID arrayAsset data is gathered when an agent or a probe does a discovery job. This typically occurs on a daily,recurring basis.Monitoring data is gathered by an agent or a probe, but is gathered much more frequently than assetdata. Typically, monitoring data is gathered every 5 minutes.Examples of monitoring data gathered by N-central• The status of fans, power supplies, temperature sensors, RAID controllers, logicaldrives, and physical drives on HP, Dell, IBM, and Intel servers• The traffic throughput on switches, routers, and servers• The status of Cisco VoIP phones, gateways, and voicemail devices• Disk, CPU, Memory, and Process metrics for Linux and OS X devicesN-central and Syslog MessagesThe N-central Windows probe receives syslog messages. These messages are typically sent from routers,switches, or firewalls when they detect an error. When the Windows probe receives a syslog message,N-central will alert you.There are two steps to take when configuring the Windows Probe to act as a syslog message receiver:1. Configure the Windows probe to monitor a syslog-based service in N-central.Just add any of the ‘FW’ services (for example, FW – Cisco, or FW – Sonicwall) in N-central to adevice.2. Configure the device to send its syslog messages to the IP address of the Windows probe.The device that is generating the syslog messages (for example, a firewall or router) needs to be configuredto send its syslog messages to the probe. As the steps for configuring that functionality varyfrom vendor to vendor, it’s recommended that you contact the vendor for specific instructions onconfiguring syslog messages for the device.- 6 -

N-central 7.2 An Introduction to SNMPSetting Up SNMP on a Windows DeviceBy default, Windows does not come with SNMP installed. However, it’s easy to install, straightforward toconfigure, and will allow you to monitor the hardware status of your Dell, HP, IBM, and Intel servers.This section will cover configuring SNMP in the Windows OS, as well as changing the SNMP properties ofa device in N-central.To install SNMP on a Windows device1. Click Start > Control Panel.2. On the Control Panel, click Add or Remove Programs.3. In the left pane, click Add/Remove Windows Components.4. Select Management and Monitoring Tools.5. Click Details.6. Select Simple Network Management Protocol, and then click OK.7. Click Next.Depending on the installation of Windows, you may need to insert the Windows installation CD in orderto complete the installation of SNMP.To configure SNMP on a Windows device1. Click Start > Run.2. Type services.msc3. Click OK.4. Double-click the SNMP Service to open the properties box.5. Click the Security tab.6. Under Accepted community names, click Add.7. Specify an SNMP community string, and then click Add.8. Select Accept SNMP packets from any host.9. Click OK.Monitoring Dell, HP, IBM, Intel and Adaptec HardwareIn addition to configuring SNMP, you must also install the following management softwarein order to monitor the hardware status of the Windows server:• Dell—OpenManage• HP—Insight Manager• IBM—ServeRAID Manager• Intel—Intel RAID Web Console• Adaptec—Storage Manager- 8 -

N-central 7.2 An Introduction to SNMPTo change the SNMP Properties of a Device in N-centralYou can easily change the SNMP properties of a device using the N-central UI. For example, you canchange the SNMP port number, SNMP version, timeout value, and number of retries.1. In the N-central UI, click the All Devices View for the appropriate customer.2. Click the device you would like to edit.3. Under Configuration Options on the Properties tab, select Enable Professional Mode, if it hasnot already been selected.Note: Selecting Professional Mode will enable all features associated with Professional Mode and willconsume one Professional Mode license.4. Under Monitoring Options, select Use SNMP.5. In the Community String field for the device, type the new Community String.6. Click Advanced Configuration to display all of the SNMP properties.7. Change the SNMP properties to match those configured on the device.8. Click Save.Why don't I see the Use SNMP option?Before you can modify the SNMP properties of a device, you need to enable the UseSNMP option. On the Properties tab, enable the Professional Mode and then enable theUse SNMP option.- 9 -

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