Add field matching rules to your lookup configuration

These attributes provide field matching rules for lookups. They can be applied to all four lookup types. Add them to the transforms.conf stanza for your lookup.

Attribute	Type	Description	Default
max_matches	Integer	The maximum number of possible matches for each value input to the lookup table from your events. Range is 1-1000. If the time_field attribute is is not specified, Splunk software uses the first <integer> entries, in file order. If the time_field attribute is specified (because it is a time-bounded lookup), Splunk software uses the first <integer> entries, in descending time order. In other words, up to <max_matches> are allowed to match. When this number is surpassed, Splunk software uses the matches closest to the lookup value.	100 if the time_field attribute is not specified. 1 if the time_field attribute is specified.
min_matches	Integer	The minimum number of possible matches for each value input to the lookup table from your events. You can use default_match to help with situations where there are fewer than min_matches for any given input.	0 for both non-time-bounded lookups and time-bounded lookups, which means nothing is output to your event if no match is found.
default_match	String	When min_matches is greater than 0 and and Splunk software finds fewer than min_matches for any given input, it provides this default_match value one or more times until the min_matches threshold is reached. Splunk software treats NULL values as matching values and does not replace them with the default_match value.	Empty string
case_sensitive_match	Boolean	Specify true to consider case when matching input lookup table fields. Specify false to ignore case when matching lookup fields. Does not apply to KV Store lookups. Reverse lookups also require reverse_lookup_honor_case_sensitive_match=true.	true
reverse_lookup_honor_case_sensitive_match	Boolean	For reverse lookups, the definition of the "input field" and the "output field" are flipped. Because the Splunk software applies case_sensitive_match to the input field, this means that reverse lookups need an additional case-sensitive match setting for the output field. When reverse_lookup_honor_case_sensitive_match=true and when case_sensitive_match=true, Splunk software performs case-sensitive matching for all fields in reverse lookups. When reverse_lookup_honor_case_sensitive_match=false, Splunk software performs case-insensitive matching for all fields in reverse lookups, even when case_sensitive_match=true. This setting does not apply to KV Store lookups. This setting may default to false in an upcoming release.	true
match_type	String	Allows non-exact matching of one or more fields arranged in a list delimited by a comma followed by a space. Format is match_type = <match_type>(<field_name1>, <field_name2>,...<field_nameN>). Set match_type to WILDCARD to apply wildcard matching, or set it to CIDR to apply CIDR matching (specifically for IP address values).	EXACT (does not need to be specified)

Example of using match_type for IPv6 CIDR match

In this example, you can use the the match_type attribute in addition to the lookup command to determine whether a specific IPv6 address is in a CIDR subnet. You can follow along with the example by performing these steps.

1. Create a lookup table in the $SPLUNK_HOME/etc/apps/search/lookups folder called ipv6test.csv that contains the following text.

ip,expected
2001:0db8:ffff:ffff:ffff:ffff:ffff:ff00/120,true

Note that the ip field in the lookup table contains the subnet value, not the IP address. This is because the match_type attribute that will be added to the transforms.conf file in the next step tells the lookup command that the value in that field is to be treated as a CIDR subnet for matching purposes.

2. Add the following entry to your local transforms.conf file, which is typically located in the $SPLUNK_HOME/etc/system/local folder. See How to edit a configuration file.

[ipv6test]
filename = ipv6test.csv
match_type=CIDR(ip)

3. Run the following search to match the IP address to the subnet.

| makeresults | eval ip="2001:0db8:ffff:ffff:ffff:ffff:ffff:ff99" | lookup ipv6test ip OUTPUT expected

The IP address is in the subnet, so search displays true in the expected field. The search results look something like this.

time	expected	ip
2020-11-19 16:43:31	true	2001:0db8:ffff:ffff:ffff:ffff:ffff:ff99

See also

Commands

iplocation

search

Functions

cidrmatch