SiteScope User's Guide

DHCP Monitor

The SiteScope DHCP Monitor checks a DHCP Server via the network. It verifies that the DHCP server is listening for requests and that it can allocate an IP address in response to a request.

Each time the DHCP Monitor runs, it returns a status and writes it in the monitoring log file. It also writes the total time it takes to receive and release an IP address in the log file.

Installation Notes

The SiteScope DHCP Monitor uses the jDHCP library, available from http://www.dhcp.org/javadhcp/. After downloading the library (either in .zip or in .tar.gz format), extract the file named JDHCP.jar and place it in the SiteScope/java/lib/ext directory, such that the file is located at SiteScope/java/lib/ext/JDHCP.jar. After installing the JDHCP.jar file, stop and restart the SiteScope service. The DHCP Monitor will not be usable until the jDHCP library is installed and SiteScope has been restarted.

Usage Guidelines

Why should I use this monitor?

If your DHCP server fails, machines relying on DHCP will be unable to acquire a network configuration when rebooting. Additionally, as DHCP address leases expire on already-configured machines, those machines will "drop off" the network when the DHCP server fails to renew their address lease. Therefore, it's important that you monitor your DHCP server(s) to ensure that they are working properly.

What should I monitor?

Most networks have a DHCP server listening for DHCP requests. This monitor will "find" DHCP servers by broadcasting a request for an IP address and waiting for a DHCP server to respond.

How should I schedule my monitors?

Your DHCP server is a critical part of providing functionality to other hosts on your network, so it should be monitored frequently (every 2-5 minutes).

Completing the DHCP Monitor Form

To display the DHCP Monitor Form, either click the Edit link for an existing DHCP Monitor in a monitor table, or click the add a Monitor link on a group's detail page and choose the "Add DHCP Monitor" link.

Complete the items on the DHCP Monitor form as follows. When the required items are complete, click the "Add Monitor" button.

Timeout: Enter the time, in seconds, to wait for an IP address.

Advanced Options

The advanced options give you the ability to customize error and warning thresholds. If you choose not to set them, SiteScope will use preset defaults if available. If a default is not available, SiteScope will not be able to utilize the condition.

Disable

Check this box to temporarily disable this monitor and any associated alerts. To enable the monitor again, clear the box.

Requested Client Address (Optional)

Optionally, the IP address to request from the DHCP server.

Verify Error

Check this box if you want SiteScope to automatically run this monitor again if it detects an error. When an error is detected, the monitor will immediately be scheduled to run again once.

Note: In order to change the run frequency of this monitor when an error is detected, use the Update every (on errors) option below.

Note: The status returned by the Verify Error run of the monitor will replace the status of the originally scheduled run that detected an error. This may cause the loss of important performance data if the data from the verify run is different than the initial error status.

Warning: Use of this option across many monitor instances may result in significant monitoring delays in the case that multiple monitors are rescheduled to verify errors at the same time.

Update Every (on error)

This options allows you to set a new monitoring interval for monitors that have registered an error condition. For example, you may want SiteScope to monitor this item every 10 minutes normally, but as often as every 2 minutes if an error has been detected. Note that this increased scheduling will also affect the number of alerts generated by this monitor.

Schedule (Optional)

By default, SiteScope's monitors are enabled every day of the week. You may, however, schedule your monitors to run only on certain days or on a fixed schedule. Choose the Edit schedule link to create or edit a monitor schedule. For information about creating schedules, read these instructions.

Monitor Description (Optional)

Enter additional information about this monitor. The Monitor Description can include HTML tags such as the <BR> <HR>, and <B> tags to control display format and style. The description will appear on the Monitor Detail page.

Report Description (Optional)

Enter a description for this monitor that will make it easier to understand what this monitor does. The description will appear on Management Reports and on the info list for a monitor.

Depends On (Optional)

To make the running of this monitor dependent on the status of another monitor or monitor group, use the drop-down list to select the monitor or group on which this monitor is dependent. Select None to remove any dependency.

Depends Condition (Optional)

If you choose to make the running of this monitor dependent on the status of another monitor, choose the status condition that the other monitor or monitor group should have in order for the current monitor to run normally. The current monitor will be run normally as long as the monitor or group on which it depends reports the condition selected in this option.

List Order (Optional)

By default, new monitors are listed last on the Monitor Detail page. You may use this drop-down list to choose a different placement for this monitor.

Error if

Set the conditions under which the DHCP Monitor should report an error status. To set the error threshold, choose milliseconds >= from the drop-down list and then, in the text entry box, enter the lowest value which should trigger a error condition . The value entered must be a whole number.

Warning if: Set the conditions under which the DHCP Monitor should report a warning status. To set the warning threshold, choose milliseconds >= from the drop-down list and then, in the text entry box, enter the lowest value which should trigger a warning condition . The value entered must be a whole number.
Good if: By default, this monitor returns a status of "good" if the monitor received a status code of 200. You can change it to return a good value based upon round-trip time.