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Create a device group based on discovery time

The ExtraHop system automatically discovers devices that send and receive traffic over the wire. In addition to the built-in groups that discover devices added in the last 24 hours and the last 7 days, you can create a custom dynamic device group that automatically adds devices that were discovered during a specific time interval.

To learn about the different time formats, see Discovery time formats.

  1. Log in to the ExtraHop system through https://<extrahop-hostname-or-IP-address>.
  2. At the top of the page, click Assets, and then click Device Groups in the left pane.
  3. In the upper right corner, click Create Device Group.
  4. In the Group Namefield, type a name for the device group.
  5. In the Group Descriptionfield, type any information that can serve as a reference for the discovery time range you specify.
  6. In the Group Type section, click Dynamic.
    The Filter Criteria section appears.
  7. Select a match operators from the drop-down list:
    Option Description
    Match All Filters only devices that match all of the specified filter criteria.
    Match Any Filters devices that matches any of the specified filter criteria.
    Match None Filters devices that do not match any of the specified filter criteria.
  8. From the categories drop-down list, click Discovery time.
  9. Select a search operator from the drop-down list:
    Option Description
    = Filters devices that are an exact match of the discovery time interval.
    ≠ Filters devices that do not exactly match the discovery time interval.
  10. In the From (In Unix time) field, complete one of the following steps:
  11. In the Until (In Unix time) field, complete of the following steps:
    • Leave this field empty to specify the present.
      Important:If the From field is empty, you cannot leave the Until field empty and must enter a fixed or relative time format.
    • Enter a fixed date in the Unix Epoch time format or type a value in the relative time format.
      Important:The format of the Until field must match the format of the From field.
  12. Click Save.

Next steps

Discovery time formats

When creating a custom device group for devices discovered during a specific time interval, the discovery time criteria must be either in Unix Epoch time or a relative time range.

Unix Epoch time

Specific dates must be converted to Unix Epoch time. This conversion helps alleviate discrepancies between time zones and different server times.

You can convert your date into a timestamp with an online tool, such as https://www.epochconverter.com/. After creating the Unix Epoch timestamp, copy and paste the timestamp into the FROM and UNTIL fields for your device group criteria. The timestamp must include milliseconds. For example, to specify August 16, 2018, 6:16:51 PM, enter 1534443411000, as shown in the following figure.



Example of a valid Unix Epoch time entry
1534238700000
Example of an invalid Unix Epoch time entry
1534238700000ms

Relative time range

To specify a point in time relative to another time point, such as one week ago from now, you must prepend a minus sign to a value and then append one of the following time units: y, M, w, d, h, m, ms. For example, type -1w to specify one week ago. You cannot specify a future time range. Relative time ranges must begin with a negative value.

The following table displays supported time units.

Time Unit Unit Suffix
Year y
Month M
Week w
Day d
Hour h
Minute m
Second s
Millisecond ms
Example of a valid relative time entry
-12h
Examples of invalid relative time entry

12h

-12H

Discovery time criteria examples

Here are examples of criteria for different discovery time ranges.

From Jan 1, 2018 12:23:23:00 UTC until now


From one month ago until one minute ago


Last modified 2023-11-07