# How To Work with Data Queries

During the past few weeks as I've made various SNMP Data Query templates I've ran into a few 'tricks' (which existing user scripts use) to make them work with most devices. It'd probably be beneficial to publish these in some manner on the documentation site so others don't have to stumble.

As you already know getting an index is the hardest thing users struggle with. I've ran across three scenarios and their solutions:

## SNMP index is present

Basically mimic the interface.xml template which comes with Cacti `(cacti/resource/snmp_queries/interface.xml)`.

SNMPWALK:

    Raw OIDs:
    .1.3.6.1.2.1.2.2.1.1.1 = INTEGER: 1
    .1.3.6.1.2.1.2.2.1.1.2 = INTEGER: 2
    .1.3.6.1.2.1.2.1.0 = INTEGER: 2

    Textual MIB names:
    IF-MIB::ifIndex.1 = INTEGER: 1
    IF-MIB::ifIndex.2 = INTEGER: 2
    IF-MIB::ifNumber.0 = INTEGER: 2

In the SNMP XML file, specify the `<oid_index>` and optional `<oid_num_indexes>` fields. For example:

    <interface>
        <name>Get SNMP Interfaces</name>
        <description>Queries a host for a list of monitorable interfaces</description>
        <oid_index>.1.3.6.1.2.1.2.2.1.1</oid_index>
        <oid_num_indexes>.1.3.6.1.2.1.2.1.0</oid_num_indexes>

        <fields>
            <ifIndex>
                <name>Index</name>
                <method>walk</method>
                <source>value</source>
                <direction>input</direction>
                <oid>.1.3.6.1.2.1.2.2.1.1</oid>
            </ifIndex>
        </fields>
    </interface>

A verbose query from inside Cacti shows the following:

    + Running data query [1].
    + Found type = '3' [snmp query].
    + Found data query XML file at 'C:/Inetpub/wwwroot/cacti/resource/snmp_queries/interface.xml'
    + XML file parsed ok.
    + Executing SNMP walk for list of indexes @ '.1.3.6.1.2.1.2.2.1.1'
    + Index found at OID: 'iso.3.6.1.2.1.2.2.1.1.1' value: '1'
    + Index found at OID: 'iso.3.6.1.2.1.2.2.1.1.2' value: '2'
    + Located input field 'ifIndex' [walk]
    + Executing SNMP walk for data @ '.1.3.6.1.2.1.2.2.1.1'
    + Found item [ifIndex='1'] index: 1 [from value]
    + Found item [ifIndex='2'] index: 2 [from value]

## SNMP Index is a STRING

Some devices (like on a F5 BigIP) use a STRING to represent the Index due to the fact it is user configurable. In this case we need Cacti to parse out the variable length Index.

Sample of a STRING Index:

Raw OID:

    .1.3.6.1.4.1.3375.2.2.10.2.3.1.1.5.76.88.87.69.66 = STRING: "LXWEB"
    .1.3.6.1.4.1.3375.2.2.10.2.3.1.1.6.69.80.88.87.69.66 = STRING: "EPXWEB"

Textual MIB names:

    F5-BIGIP-LOCAL-MIB::ltmVirtualServStatName."LXWEB" = STRING: LXWEB
    F5-BIGIP-LOCAL-MIB::ltmVirtualServStatName."EPXWEB" = STRING: EPXWEB

Next we need to define a OID/REGEXP that will look for the start of the STRING and create the Index. In this case the regexp "^.{32}" matches the first 32 characters beginning at the start of the OID -- this is the length of the OID from the leading dot up to the start of the index. Then the capturing parens "(.*)" grab the remainder of the OID as a backreference. Use the following SNMP XML script:

    <interface>
        <name>Get F5 Big-IP Load Balancer Virtual Server Statistics</name>
        <oid_index>.1.3.6.1.4.1.3375.2.2.10.2.3.1.1</oid_index>
            <oid_index_parse>OID/REGEXP:^.{32}(.*)</oid_index_parse>
            <index_order>vsIndex</index_order>
            <index_order_type>alphabetic</index_order_type>

            <fields>
            <vsIndex>
                <name>Index</name>
                <source>index</source>
                <direction>input</direction>
            </vsIndex>
        </fields>
    </interface>

After creating the Data Query Data & Graph templates in Cacti a verbose query will spit out the following:

    + Running data query [20].
    + Found type = '3' [snmp query].
    + Found data query XML file at 'C:/Inetpub/wwwroot/cacti/resource/snmp_queries/f5_bigip_vs.xml'
    + XML file parsed ok.
    + Executing SNMP walk for list of indexes @ '.1.3.6.1.4.1.3375.2.2.10.2.3.1.1'
    + Index found at OID: 'enterprises.3375.2.2.10.2.3.1.1.5.76.88.87.69.66' value: 'LXWEB'
    + Index found at OID: 'enterprises.3375.2.2.10.2.3.1.1.6.69.80.88.87.69.66' value: 'EPXWEB'
    + index_parse at OID: 'enterprises.3375.2.2.10.2.3.1.1.5.76.88.87.69.66' results: '5.76.88.87.69.66'
    + index_parse at OID: 'enterprises.3375.2.2.10.2.3.1.1.6.69.80.88.87.69.66' results: '6.69.80.88.87.69.66'
    + Inserting index data for field 'vsIndex' [value='5.76.88.87.69.66']
    + Inserting index data for field 'vsIndex' [value='6.69.80.88.87.69.66']

## SNMP Index does not exist

Some devices do not offer a traditional Index OID to query. Here we need to create/fake the index for Cacti. This is accomplished once again with a simple REGEX to split off the last OID (or middle, etc) to create the index for cacti.

SNMPWALK:

Raw OIDs:

    .1.3.6.1.2.1.7.1.0 = Counter32: 69367
    .1.3.6.1.2.1.7.2.0 = Counter32: 11
    .1.3.6.1.2.1.7.3.0 = Counter32: 0
    .1.3.6.1.2.1.7.4.0 = Counter32: 64392

Textual MIB name:

    UDP-MIB::udpInDatagrams.0 = Counter32: 69458
    UDP-MIB::udpNoPorts.0 = Counter32: 11
    UDP-MIB::udpInErrors.0 = Counter32: 0
    UDP-MIB::udpOutDatagrams.0 = Counter32: 64471

Consulting the MIB file for these OIDs, we know that the associated index will always be "0" for each OID. We'll want to split this off with the REGEX.

Create the following SNMP XML file:

    <interface>
        <name>Get RFC1213 Stats</name>
        <description>Management Information Base for Network Management of TCP/IP-based internets</description>
        <oid_index>.1.3.6.1.2.1.7.2</oid_index>
        <oid_index_parse>OID/REGEXP:.*\.([0-9]{1,2})$</oid_index_parse>
        <index_order>Index</index_order>
        <index_order_type>alphabetic</index_order_type>

        <fields>
            <Index>
                <name>Index</name>
                <source>index</source>
                <direction>input</direction>
            </Index>
        </fields>
    </interface>

Once all of the required templates have been created, a verbose query from Cacti results in the following:

    + Running data query [23].
    + Found type = '3' [snmp query].
    + Found data query XML file at 'C:/Inetpub/wwwroot/cacti/resource/snmp_queries/RFC1213.xml'
    + XML file parsed ok.
    + Executing SNMP walk for list of indexes @ '.1.3.6.1.2.1.7.2'
    + Index found at OID: 'iso.3.6.1.2.1.7.2.0' value: '11'
    + index_parse at OID: 'iso.3.6.1.2.1.7.2.0' results: '0'
    + Inserting index data for field 'Index' [value='0']

## A note on Textual SNMP MIBS and SPINE

Please be aware the SPINE does not parse out textual Mibs. This means that if you were to use an OID that contained a string reference rather than numerical this will cause Graphs to fail as they will not be generated due to spine not receiving a value at each poll

Example of a bad OID reference for spine:

    interfaces.mib.1.1.1.1.1

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