SNMP probe parameters
Summarize
Summary of SNMP probe parameters
This documentation describes the parameters you can configure for SNMP probes in ServiceNow, specifically for the Zurich release. These parameters control how SNMP queries are performed on network devices, enabling customization of probe behavior such as OID selection, timeouts, request intervals, and request methods (GETBULK or GETNEXT). Proper configuration of these parameters helps optimize SNMP data collection, improve accuracy, and reduce load on devices and MID Servers.
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Key Parameters and Their Use
- oidspeclist: Defines the OIDs to walk or query, supporting single OIDs or tables with child OIDs and filters for targeted data collection.
- source: Specifies the IP address or hostname of the SNMP target device (required).
- index: Used for Cisco-style community string indexing, typically for VLAN interrogation, defaulting to 0.
- timeout and establishedsessiontimeout: Control how long the probe waits for responses, overriding MID Server default timeouts for improved reliability.
- requestinterval and requestdelay: Manage the timing between SNMP requests to balance query speed and device impact.
- debug: Enables debug logging to assist in troubleshooting probe issues.
- resultformat: Returns JSON formatted payloads for specific probes to prevent sensor failures due to large data sets; should not be altered.
- usegetbulk: Enables more efficient retrieval of tabular data using SNMP GETBULK requests instead of multiple GETNEXT requests. When enabled, some timing parameters are ignored and replaced by retries.
- usegetscalar: Enables simplified retrieval of scalar SNMP values, also altering which timing parameters are used.
- retries: Defines the number of retry attempts for GETBULK or GETNEXT requests when using usegetbulk or usegetscalar, improving robustness.
Practical Implications for ServiceNow Customers
By configuring SNMP probe parameters appropriately, you can tailor SNMP data collection to your network environment, targeting specific OIDs or tables with filters, optimizing timeouts and request pacing, and choosing between efficient bulk retrieval or simplified scalar queries. This leads to more accurate and complete discovery data while minimizing unnecessary network traffic and MID Server load. The built-in JSON result format for certain probes ensures stability even with large datasets.
Note that some parameters, such as credentialid and credentialtag, are for internal use only and not supported for configuration.
This list of parameters may be passed to the SNMP probes.
For instructions on configuring probe parameters, see Set probe parameters.
| Parameter | Description | Default Value |
|---|---|---|
| oid_spec_list | A list of OID specifications, one per line. Each specification must be in one of the following two forms:
{OID Children} refers to a comma-delimited list of child nodes within the entries for the given table. For example, "ifEntry.ifIndex,ifEntry.ifDescr,ifEntry.ifType" are OID children of the table "iso.org.dod.internet.mgmt.mib-2.interfaces.ifTable". As a convenience, the table entry prefix may be left off. (The preceding children could be specified as "ifIndex,ifDescr,ifType".) Any child may include a filter qualifier in parentheses. For example, the child "entPhysicalContainedIn(=0)" specifies returning table entries only if the value of "entPhysicalContainedIn" equals 0. The
operators supported in the expression are:
If more than one child has a filter expression, a match on any one of the children causes that entry to be read. Any content including and after a "//" is ignored (comments). Any OID that does not start with "1.3.6.1" or "iso.org.dod.internet" automatically prefaces with "1.3.6.1." as a convenience. |
required |
| source | The IP address or host name of the device to query SNMP on. | required |
| index | The index to apply after the community string, for Cisco-style community string indexing (for VLAN interrogation). | 0 |
| credential_id | The sys_id of a specific credential that is preferred for use above the rest. This parameter is for internal use only and is not supported. | none |
| credential_tag | The credential tag that must be used. This parameter is for internal use only and is not supported. | none |
| timeout | The timeout value (in milliseconds) to wait for a response, instead of the default. You can use this parameter to override the mid.snmp.request.timeout SNMP MID Server configuration parameter. Note: When use_getbulk is set to true,
the timeout value is for an individual GETBULK request. |
1500 |
| established_session_timeout | The interval (in milliseconds) to wait for a response after at least one response has been received. Longer values can be useful for collecting complete and accurate data. You can use this parameter to override the mid.snmp.session.timeout SNMP MID Server configuration parameter. | 500 |
| debug | Enables debug logging. Set to true for debug mode. | false |
| request_interval | The interval (in milliseconds) between successive requests for an OID when a response has not been received, until the timeout (or established_session_timeout) value is reached. If this value is set to at least as long as the timeout (or established_session_timeout) value, then only a single request is sent for any particular OID. If you change the timeout (or established_session_timeout) value, adjust the request_interval at the same time to avoid sending too many or too few requests for the same OID, as appropriate for a given environment. | 400 |
| request_delay | The interval (in milliseconds) between the receipt of a response and the transmission of the next request. The default is 0 (no delay). This value may be set to slow the overall rate of an SNMP query. | 0 |
| result_format | Returns JSON formatted payloads for these probes:
Warning: Use of this parameter with any other probes causes the sensor to fail. |
JSON |
| use_getbulk | Enables the use of SNMP GETBULK requests to retrieve tabular data from SNMP
devices instead of using multiple SNMP GETNEXT requests. For tabular data,
GETBULK is more efficient. Regardless of the request type, certain devices may
not return any results when they are busy with other tasks. This parameter is
used to configure at the probe level. GETBULK can also be set for an individual
MID Server or globally for all MID servers. Settings are listed in the order of
precedence:
The established_session_timeout, request_interval, and request_delay parameters are ignored when use_getbulk is set to true. Instead, the retries parameter is available. The timeout configuration is the same one used by use_getscalar. By default, the following probes use GETBULK requests (the parameter value is
true).
Note: These probes have a timeout value of 5000. |
false |
| use_getscalar | Enables the use of simplified retrieval and handling of scalar values from
SNMP devices. The established_session_timeout, request_interval, and request_delay parameters are ignored when use_getscalar is set to true. Instead, the retries and timeout parameters are available. The timeout configuration is the same one used by use_getbulk. |
false |
| retries | The number of additional attempts Discovery makes to complete an individual GETBULK request (see use_getbulk) or a GETNEXT request when the use_getscalar parameter is set to true. | 2 |