Discovery processes can occupy significant resources within the network when discovery is taking place. You can avoid possible interference with latency-sensitive network applications by creating time periods when NetMRI will not communicate with devices or networks for discovery. These time periods are called discovery blackout periods. You can create discovery blackout periods for each discovery range you define in NetMRI. Discovery blackout periods are optional and can be enabled and configured, or disabled, at any time. All communications are stopped with a given device, including but not limited to the following:

• SNMP
• SSH
• Telnet
• Ping
• Traceroute

A second blackout type, change blackout, allows NetMRI to enforce blackouts for CLI interaction, scheduled or run-now job executions, Telnet/SSH proxy, and port control UI features. Change blackouts will allow read-only discovery, the device changes detection, and device analysis for Issues without permitting any CLI communication or configuration changes. Change blackouts typically disallow operations such as enabling or disabling interfaces on devices.

Discovery blackouts and change blackouts can be applied to the following:

• Globally across the entire NetMRI deployment. For more information, see the next section, "Configuring a Global Discovery Blackout or Change Blackout".
• Discovery IP ranges. For more information, see Configuring Discovery Ranges.
• Strategic individual devices. For more information, see Creating Blackouts for Individual Devices.
• Device Groups. For more information, see Creating Device Groups.

Discovery tasks may already be running when a blackout period takes effect. Current tasks will not be interrupted and will complete within their time. NetMRI will not activate new discovery tasks on the chosen network, device group, or individual device during the blackout period.

Configuring a Global Discovery Blackout or Change Blackout

You can separately configure discovery blackouts and change blackouts. No dependencies exist between blackout types. You may configure either type without defining new settings for the other type. At the Global level, discovery blackouts and change blackouts apply across all network views, discovery ranges, device groups, and devices unless otherwise disabled at the range or device group level.

Complete the following:

1. Choose Settings icon > Setup > Collection and Groups.
2. On the Global page (which appears by default), check the Enable Discovery Blackout check box and click its Scheduling icon. The Discovery Blackout Scheduling gadgets appear.
   • In the Recurrence Pattern drop-down, choose how often you want to execute the blackout period. You can select Once, Daily, Weekly, or Monthly.
   • If you choose Once, complete the following:
     • Choose an Execution Time from the drop-down list.
     • Enter the date of the blackout, in the Day_of_ field.
     • Specify the Duration: 10 or more Minutes, Hours, or Days.
   • If you choose Daily, click either Every Day or Every Weekday.
     
     • Choose an Execution Time from the drop-down list.
     • Specify the Duration: 10 or more Minutes, Hours, or Days.
   • If you choose Weekly, complete the following:
     • Choose an Execution Time from the drop-down list.
     • Check the check boxes for one or more days from Sunday through Saturday.
     • Specify the Duration: 10 or more Minutes, Hours, or Days.
   • If you choose Monthly, complete the following:
     • Choose an Execution Time from the drop-down list.
     • Day __ of every __ month(s): Specify for the discovery blackout to be executed on day-of-month X of every Y month. Month numbering starts with January. You can see some examples below.
       Day 5 of every 1 month(s): means the blackout is executed on the 5th of the current and each next month.
       Day 5 of every 2 month(s): means the blackout is executed on the 5th of January, March, May, July, and so on.
     • Specify the Duration: 10 or more Minutes, Hours, or Days.
3. If necessary, select the Enable Change Blackout check box and click its Scheduling icon. The Discovery Blackout Scheduling gadgets appear. Follow the steps above to define the change blackout schedule.
4. Click Save.