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Snmp queries to devices

Snmp queries to devices

Dec 16, 2021

The most widely used SNMP versions are SNMP version 1 (SNMPv1) and SNMP version 2 (SNMPv2). SNMP version 3 (SNMPv3) includes important changes with respect to previous versions, especially in security issues; however, its acceptance has been very low due to some implementation problems and incompatibilities.

 

  • If you’re using SNMPv1 or v2: Is the device configured with the correct community string in LogicMonitor (either at the global, group or device level)? If no community string is set, LogicMonitor defaults to using public. Note: Some Linux distributions significantly restrict which metrics are exposed if the community string is set to “public”. Therefore, we recommend you set your community string to something else.  See the section below to verify that your device has the correct community string set.

  • If you’re using SNMPv3: Is the device configured with the correct authpass, privpass and username (either at the global, group or device level)? See the section below to verify that your device has the correct v3 credentials set.
    Can queries from the collector device reach the monitored device? 

 

What is snmpwalk?

snmpwalk is the name given to an SNMP application that executes multiple GETNEXT requests automatically. The SNMP GETNEXT request is used to query a device and grab SNMP data from a device. The snmpwalk command is used because it allows the user to chain GETNEXT requests together without having to enter unique commands for each OID or node within a subtree.

The snmpwalk is issued to the root node of the subtree so that information is collected from each connected node. This gives you an efficient way to collect information from a variety of devices such as routers and switches. The information it collects comes in the form of OIDs. An OID is an object that is part of the MIB within an SNMP-enabled device.

snmpwalk help menu.

[root@cnvtmxomk01 snmp]# snmpwalk -H Configuration directives understood:   In snmpwalk.conf and snmpwalk.local.conf:     includeRequested         (1|yes|true|0|no|false)     excludeRequested         (1|yes|true|0|no|false)     printStatistics          (1|yes|true|0|no|false)     dontCheckOrdering        (1|yes|true|0|no|false)     timeResults              (1|yes|true|0|no|false)     timeResultsSingle        (1|yes|true|0|no|false)   In snmp.conf and snmp.local.conf:     extraX509SubDir          string     x509CRLFile              string     tlsAlgorithms            string     localCert                string     peerCert                 string     alias                    NAME TRANSPORT_DEFINITION     doDebugging              (1|0)     debugTokens              token[,token...]     logTimestamp             (1|yes|true|0|no|false)     logOption                string     mibdirs                  [mib-dirs|+mib-dirs|-mib-dirs]     mibs                     [mib-tokens|+mib-tokens]     mibfile                  mibfile-to-read     showMibErrors            (1|yes|true|0|no|false)     commentToEOL             (1|yes|true|0|no|false)     strictCommentTerm        (1|yes|true|0|no|false)     mibAllowUnderline        (1|yes|true|0|no|false)     mibWarningLevel          integerValue     mibReplaceWithLatest     (1|yes|true|0|no|false)     printNumericEnums        (1|yes|true|0|no|false)     printNumericOids         (1|yes|true|0|no|false)     escapeQuotes             (1|yes|true|0|no|false)     dontBreakdownOids        (1|yes|true|0|no|false)     quickPrinting            (1|yes|true|0|no|false)     numericTimeticks         (1|yes|true|0|no|false)     oidOutputFormat          integerValue     suffixPrinting           integerValue     extendedIndex            (1|yes|true|0|no|false)     printHexText             (1|yes|true|0|no|false)     printValueOnly           (1|yes|true|0|no|false)     dontPrintUnits           (1|yes|true|0|no|false)     hexOutputLength          integerValue     dumpPacket               (1|yes|true|0|no|false)     reverseEncodeBER         (1|yes|true|0|no|false)     defaultPort              integerValue     defCommunity             string     noTokenWarnings          (1|yes|true|0|no|false)     noRangeCheck             (1|yes|true|0|no|false)     persistentDir            string     tempFilePattern          string     noDisplayHint            (1|yes|true|0|no|false)     16bitIDs                 (1|yes|true|0|no|false)     clientaddr               string     clientaddrUsesPort       (1|yes|true|0|no|false)     serverSendBuf            integerValue     serverRecvBuf            integerValue     clientSendBuf            integerValue     clientRecvBuf            integerValue     noPersistentLoad         (1|yes|true|0|no|false)     noPersistentSave         (1|yes|true|0|no|false)     noContextEngineIDDiscovery (1|yes|true|0|no|false)     timeout                  integerValue     retries                  integerValue     defDomain                application domain     defTarget                application domain target     dontLoadHostConfig       (1|yes|true|0|no|false)     defSecurityModel         string     tsmUseTransportPrefix    (1|yes|true|0|no|false)     defAuthType              MD5|SHA     defPrivType              DES|AES     defSecurityName          string     defContext               string     defPassphrase            string     defAuthPassphrase        string     defPrivPassphrase        string     defAuthMasterKey         string     defPrivMasterKey         string     defAuthLocalizedKey      string     defPrivLocalizedKey      string     defVersion               1|2c|3     defSecurityLevel         noAuthNoPriv|authNoPriv|authPriv     trustCert                trustCert FINGERPRINT|FILENAME   In snmpapp.conf and snmpapp.local.conf:     defDomain                application domain     defTarget                application domain target     engineID                 string     engineIDType             num     engineIDNic              string [root@cnvtmxomk01 snmp]#

 

 

How to Use SNMPWALK to Retrieve the System Information

In this section, we will show you how to use the SNMPWALK command in Linux to retrieve the system information.

You can use the following options with the SNMPWALK command to retrieve system information, this with snmp version 1 and 2:

  • -v: Specify the SNMP version.

  • -c: Specify the community string which you have configured on the SNMP.

  • hostname: Specify the hostname or IP address of the system where the SNMP agent is installed.

  • OID: Specify the OID to return all SNMP objects.

 

snmpwalk -v2c -c <communuty> <ip_device>

 

To validate that the machine responds to snmpv3 you must execute the following command:

snmpwalk -v3 -u username -a MD5|SHA -A authphrase -x DES|AES -X privaphrase -l noAuthNoPriv|authNoPriv|authPriv ipaddress|host

 Example:

snmpwalk -v3 -u 'La$taM0mk' -a SHA -A 'j4JJXzz_#Pcok1' -x AES -X 'lWts_Pok1#0n1r' -l AuthPriv Node_test_LATAM

 

Output:

The following example CLI command will return the IPS temperature information: Command:snmpwalk -v 2c -c tinapc <IP address> 1.3.6.1.4.1.10734.3.5.2.5.5 Command Explanation: In this case the CLI command breaks down as following; snmpwalk = SNMP application -v 2c = specifies what SNMP version to use (1, 2c, 3) -c tinapc = specifies the community string. Note: The IPS has the SNMP read-only community string of "tinapc" <IP address> = specifies the IP address of the IPS device 1.3.6.1.4.1.10734.3.5.2.5.5 = OID parameter for the IPS temperature information Results: SNMPv2-SMI::enterprises.10734.3.5.2.5.5.1.0 = INTEGER: 27 SNMPv2-SMI::enterprises.10734.3.5.2.5.5.2.0 = INTEGER: 50 SNMPv2-SMI::enterprises.10734.3.5.2.5.5.3.0 = INTEGER: 55 SNMPv2-SMI::enterprises.10734.3.5.2.5.5.4.0 = INTEGER: 0 SNMPv2-SMI::enterprises.10734.3.5.2.5.5.5.0 = INTEGER: 85 Results Explanation: SNMPv2-SMI::enterprises.10734.3.5.2.5.5.1.0 = INTEGER: 27 = The chassis temperature (27° Celsius / 80.6° Fahrenheit) SNMPv2-SMI::enterprises.10734.3.5.2.5.5.2.0 = INTEGER: 50 = The major threshold value for chassis temperature (50° Celsius / 122° Fahrenheit) SNMPv2-SMI::enterprises.10734.3.5.2.5.5.3.0 = INTEGER: 55 = The critical threshold value of chassis temperature (55° Celsius / 131° Fahrenheit) SNMPv2-SMI::enterprises.10734.3.5.2.5.5.4.0 = INTEGER: 0 = The minimum value of the chassis temperature range ( 0° Celsius / 32° Fahrenheit) SNMPv2-SMI::enterprises.10734.3.5.2.5.5.5.0 = INTEGER: 85 = The maximum value of the chassis temperature range (85° Celsius / 185° Fahrenheit)