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Manual Chapter: Configuration Guide for the BIG-IP® Link Controller: Configuring Monitors
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8

Configuring Monitors


Introducing monitors

An important feature of the Link Controller is load-balancing tools called monitors. Monitors verify connections on pools and virtual servers. A monitor can be either a health monitor or a performance monitor, designed to check the status of a pool, or virtual server on an ongoing basis, at a set interval. If a pool or virtual server being checked does not respond within a specified timeout period, or the status of a pool or virtual server indicates that performance is degraded, and the Link Controller can redirect the traffic to another resource.

Some monitors are included as part of the Link Controller, while other monitors are user-created. Monitors that the Link Controller provides are called pre-configured monitors. User-created monitors are called custom monitors. For more information on pre-configured and custom monitors, see Understanding pre-configured and custom monitors .

Before configuring and using monitors, it is helpful to understand some basic concepts regarding monitor types, monitor settings, and monitor implementation.

  • Monitor types
    Every monitor, whether pre-configured or custom, is a certain type of monitor. Each type of monitor checks the status of a particular protocol, service, or application. For example, one type of monitor is HTTP. An HTTP type of monitor allows you to monitor the availability of the HTTP service on a pool, pool member, or virtual server. A WMI type of monitor allows you to monitor the performance of a pool, or virtual server that is running the Windows Management Instrumentation (WMI) software. An ICMP type of monitor simply determines whether the status of a resource is up or down. For more information on monitor types, see Summary of monitor types and Configuring monitor settings .
  • Monitor settings
    Every monitor consists of settings with values. The settings and their values differ depending on the type of monitor. In some cases, the Link Controller assigns default values. For example, the following are the default values for the ICMP-type monitor:
    • Interval: 30 seconds
    • Timeout: 120 seconds
    • Transparent: No
    • These settings specify that an ICMP type of monitor is configured to check the status of an IP address every 30 seconds, and to time out every 120 seconds. For more information on monitor settings, see Summary of status types and Configuring monitor settings .

  • Monitor implementation
    The task of implementing a monitor varies depending on whether you are using a pre-configured monitor or creating a custom monitor. If you want to implement a pre-configured monitor, you need only associate the monitor with a pool or virtual server. If you want to implement a custom monitor, you must first create the custom monitor, and then associate it with a pool or virtual server. For more information on implementing a monitor, see Understanding pre-configured and custom monitors and Creating a custom monitor .

Summary of monitor types

The Link Controller includes many different types of monitors, each designed to perform a specific type of monitoring. The monitors fall into three categories: simple, extended content verification (ECV), and extended application verification (EAV). Simple monitors check the health of a resource by sending a packet using the specified protocol, and waiting for a response from the resource. If the monitor receives a response, then the health check is successful and the resource is considered up. ECV monitors check the health of a resource by sending a query for content using the specified protocol, and waiting to receive the content from the resource. If the monitor receives the correct content, then the health check is successful and the resource is considered up. EAV monitors check the health of a resource by exercising the specified application. If the monitor receives the correct response, then the health check is successful and the resource is considered up.

Table 8.1 describes the types of monitors that you can apply to your load balancing resources.

Table 8.1 Monitor types available on a GTM system
Monitor Category
Monitor Type
Description
Simple
ICMP
Checks the status of a resource, using Internet Control Message Protocol (ICMP).
Simple
TCP Echo
Checks the status of a resource, using Transmission Control Protocol (TCP).
ECV
TCP
Verifies the Transmission Control Protocol (TCP) service by attempting to receive specific content from a resource.
ECV
HTTP
Verifies the Hypertext Transfer Protocol (HTTP) service by attempting to receive specific content from a web page.
ECV
HTTPS
Verifies the Hypertext Transfer Protocol Secure (HTTPS) service by attempting to receive specific content from a web page protected by Secure Socket Layer (SSL) security.
EAV
BIG IP Link
Acquires data captured through monitors managed by a BIG-IP Link Controller.
EAV
FTP
Verifies the File Transfer Protocol (FTP) service by attempting to download a specific file to the /var/tmp directory on the system. Once downloaded successfully, the file is not saved.
EAV
SNMP Link
Acquires data captured through SNMP traps.

Summary of status types

When a monitor attempts to verify the availability of a resource, it returns a status of that resource to the Link Controller. This status appears as a status code in the Configuration utility. A status code is a specific color that denotes the health of a given resource. Using these status codes, you can quickly determine the health of any monitored resource.

The types of status codes available for a resource are:

  • Blue. A blue status code indicates that the resource has not been checked. This status often appears when you first add a resource into the Configuration utility.
  • Green. A green status code indicates that the resource is available and operational. The Link Controller uses this resource to manage traffic as appropriate.
  • Red. A red status code indicates that the resource did not respond as expected to the monitor. The Link Controller considers resources with a red status code as down and does not use that resource when managing network traffic.
  • Yellow. A yellow status code indicates that the resource is operational, but has exceeded one of its established bandwidth thresholds. The Link Controller only uses a link that has a yellow status code if no other link is available (for example, all other links have a status code of red or blue).
  • Gray. A gray status code indicates that the resource is unavailable for configuration through this Link Controller. For example, if a wide IP was removed from the Configuration utility, but its corresponding configuration settings had not been deleted, the link would have a gray status code.

Understanding pre-configured and custom monitors

When you want to monitor the health or performance of pool members or virtual servers, you can either use a pre-configured monitor, or create and configure a custom monitor.

Using pre-configured monitors

For a subset of monitor types, the Link Controller includes a set of pre-configured monitors. A pre-configured monitor is an existing monitor that the Link Controller provides for you, with its settings already configured. You cannot modify pre-configured monitor settings, as they are intended to be used as is. The purpose of a pre-configured monitor is to eliminate the need for you to explicitly create one. You use a pre-configured monitor when the values of the settings meet your needs, as is.

The names of the pre-configured monitors that the Link Controller includes are:

  • big ip link
  • gateway icmp
  • http
  • https
  • icmp
  • snmp link
  • tcp
  • tcp_echo

An example of a pre-configured monitor is the icmp monitor. If the default values of this monitor meet your needs, you simply assign the icmp pre-configured monitor directly to a pool or virtual server. In this case, you do not need to use the Monitors screens, unless you simply want to view the default settings of the pre-configured monitor.

If you do not want to use the values configured in a pre-configured monitor, you can create a custom monitor.

Using custom monitors

A custom monitor is a monitor that you create based on one of the allowed monitor types.You create a custom monitor when the values defined in a pre-configured monitor do not meet your needs, or no pre-configured monitor exists for the type of monitor you are creating. (For information on monitor types, see Summary of monitor types .)

Importing settings from a pre-configured monitor

If a pre-configured monitor exists that corresponds to the type of custom monitor you are creating, you can import the settings and values of that pre-configured monitor into the custom monitor. You are then free to change those setting values to suit your needs. For example, if you create a custom monitor called my_icmp, the monitor can inherit the settings and values of the pre-configured monitor icmp. This ability to import existing setting values is useful when you want to retain some setting values for your new monitor but modify others.

The following list shows an example of a custom ICMP-type monitor called demo_icmp, which is based on the pre-configured monitor icmp. Note that the Interval value has been changed to 60. The other settings retain the values defined in the pre-configured monitor.

  • Name: demo_icmp
  • Type: ICMP
  • Interval: 60
  • Timeout: 180
  • Transparent: No

Importing settings from a custom monitor

You can import settings from another custom monitor instead of from a pre-configured monitor. This is useful when you would rather use the setting values defined in another custom monitor, or when no pre-configured monitor exists for the type of monitor you are creating. For example, if you create a custom monitor called my_oracle_server2, you can import settings from an existing Oracle-type monitor such as my_oracle_server1. In this case, because the Link Controller does not provide a pre-configured Oracle-type monitor, a custom monitor is the only kind of monitor from which you can import setting values.

Selecting a monitor is straightforward. Like icmp, each of the monitors has a Type setting based on the type of service it checks, for example, http, https, ftp, pop3, and takes that type as its name. (Exceptions are port-specific monitors, like the external monitor, which calls a user-supplied program.)

For procedures on selecting and configuring a monitor, see Creating a custom monitor .

Importing settings from a monitor template

If no pre-configured or custom monitor exists that corresponds to the type of monitor you are creating, the Link Controller imports settings from a monitor template. A monitor template is an abstraction that exists within the Link Controller for each monitor type, and contains a group of settings and default values. A monitor template merely serves as a tool for the Link Controller to use for importing settings to a custom monitor when no monitor of that type already exists.

Creating a custom monitor

When you create a custom monitor, you use the Configuration utility to: give the monitor a unique name, specify a monitor type, and, if a monitor of that type already exists, import settings and their values from the existing monitor. You can then change the values of any imported settings.

You must base each custom monitor on a monitor type. When you create a monitor, the Configuration utility displays a list of monitor types. To specify a monitor type, select the one that corresponds to the service you want to check. For example, if you want to want to create a monitor that checks the health of the HTTP service on a pool, you choose HTTP as the monitor type.

If you want to check more than one service on a pool or virtual server (for example HTTP and HTTPS), you can associate more than one monitor on that pool or virtual server. For more information, see Chapter 9, Inbound Load Balancing .

Checking services is not the only reason for implementing a monitor. If you want to verify only that the destination IP address is alive, or that the path to it through a transparent virtual server is alive, use one of the simple monitors, icmp or tcp_echo. Or, if you want to verify TCP only, use the monitor tcp.

Note

Before creating a custom monitor, you must decide on a monitor type. For information on monitor types, see Configuring monitor settings .

To create a custom monitor

  1. On the Main tab of the navigation pane, expand Link Controller and then click Monitors.
    The monitors screen opens.
  2. Click the Create button.
    The create monitor screen opens.
  3. In the Name box, type a name for the monitor.
  4. For the Type setting, select the type of monitor that you want to create.
    If a monitor of that type already exists, Import Settings appears.
  5. In the Configuration section of the screen, select Advanced. This allows you to modify additional default settings.
  6. Configure all settings shown.
  7. Click the Finished to save your changes.

Configuring monitor settings

Before you can create a custom monitor, you must select a monitor type. Monitors types fall into three categories:

  • Simple monitors
    These are health monitors that monitor the status of a resource.
  • Extended Content Verification (ECV) monitors
    These are health monitors that verify service status by retrieving specific content from pool members or virtual servers.
  • External Application Verification (EAV) monitors
    These are health or performance monitors that verify service status by executing remote applications, using an external service-checker program.

Simple monitors

Simple monitors are those that check the status of a resource. The simple monitor types are:

  • ICMP
  • Gateway ICMP
  • TCP Echo
  • BIG-IP Link
  • SNMP Link

The GTM system provides a set of pre-configured simple monitors: icmp, gateway_icmp, tcp_echo, and tcp_half_open. You can either use these pre-configured monitors as is, or create custom monitors of these types.

The following sections describe each type of simple monitor and show the pre-configured monitor for each type. Note that each pre-configured monitor consists of settings and their values. The boldfaced type within each pre-configured monitor serves to distinguish the settings from their corresponding values.

ICMP

Using an ICMP type of monitor, you can use Internet Control Message Protocol (ICMP) to make a simple resource check. The check is successful if the monitor receives a response to an ICMP_ECHO datagram. The following list shows the settings and their values for the pre-configured monitor icmp:

  • Name: ICMP
  • Type: ICMP
  • Interval: 30 seconds
  • Timeout: 120 seconds
  • Transparent: No
  • Alias Address: * All Addresses

The Transparent mode is an option for ICMP-type monitors. When you set this mode to Yes, the monitor pings the resource with which the monitor is associated. For more information about Transparent mode, refer to Using transparent and reverse modes .

Gateway ICMP

A Gateway ICMP type of monitor has a special purpose. You use this monitor for a pool that implements gateway failsafe for high availability.

A Gateway ICMP monitor functions the same way as an ICMP monitor, except that you can apply a Gateway ICMP monitor to a pool. (Remember that you can apply an ICMP monitor to a resource only and not a pool member.) The following list shows the settings and their values for the pre-configured gateway_icmp monitor.

  • Name: Gateway ICMP
  • Type: Gateway ICMP
  • Interval: 30 seconds
  • Timeout: 120 seconds
  • Transparent: No
  • Alias Address: * All Addresses
  • Alias Service Port: * All Ports

TCP Echo

With a TCP Echo type of monitor, you can verify Transmission Control Protocol (TCP) connections. The check is successful if the Link Controller receives a response to a TCP Echo message. The TCP Echo type also supports Transparent mode. In this mode, the resource with which the monitor is associated is pinged through to the destination resource. (For more information about Transparent mode, see Using transparent and reverse modes .)

To use a TCP Echo monitor type, you must ensure that TCP Echo is enabled on the resources being monitored. The following list shows the settings for the pre-configured monitor tcp_echo:

  • Name: TCP Echo
  • Type: TCP Echo
  • Interval 30 seconds
  • Timeout 120 seconds
  • Alias Address: * All Addresses

BIG IP Link

If you employ the Link Controller in a network that contains a Link Controller, you must use assign a BIG IP Link monitor to the Link Controller. In fact, this monitor is automatically assigned to the Link Controller if you do not do so manually.

The BIG IP Link monitor gathers metrics and statics information that the Link Controller acquires through the monitoring of its own resources.

The following list shows the settings and default values of a BIG IP Link-type monitor:

  • Name: my_bigip_link
  • Type: BIG IP Link
  • Interval: 10 seconds
  • Timeout: 30 seconds
  • Probe Interval: 1 second
  • Probe Timeout: 1 second
  • Probe Attempts: 1
  • Minimum Required Successful Attempts: 1
  • Alias Address: * All Addresses
  • Alias Service Port: * All Ports

SNMP Link

You use an SNMP Link type of monitor to check the performance of links that are running an SNMP agent.

The GTM system provides a pre-configured SNMP monitor named snmp_link. The following list shows the settings and values of the snmp_link pre-configured monitor:

  • Name: snmp_link
  • Type: SNMP Link
  • Interval: 10 seconds
  • Timeout: 30 seconds
  • Probe Interval: 1 second
  • Probe Timeout; 1 second
  • Probe Attempts: 1
  • Minimum Required Successful Attempts: 1
  • Alias Addresses: * All Addresses
  • Alias Service Port: * All Ports

Performance monitors are generally used with dynamic ratio load balancing. For more information on performance monitors and dynamic ratio load balancing, see Chapter 9, Inbound Load Balancing .

Note

Unlike health monitors, performance monitors do not report on the status of pool, pool member, or virtual server.

Pre-configured monitors are not user-modifiable. Thus, if you want to change the values for the SNMP Link monitor settings, you must create an SNMP Link-type custom monitor.

Extended Content Verification (ECV) monitors

ECV monitors use Send String and Receive String settings in an attempt to retrieve explicit content from resources. The Link Controller provides the pre-configured monitors tcp, http, and https for these ECV monitor types:

  • TCP
  • HTTP
  • HTTPS

You can either use the pre-configured ECV monitors as is, or create custom monitors from these monitor types.

The following sections describe each type of ECV monitor and show the pre-configured monitor for each type. Note that each pre-configured monitor consists of settings and their values. The boldfaced type within each pre-configured monitor serves to distinguish the settings from their corresponding values.

TCP

A TCP type of monitor attempts to receive specific content sent over TCP. The check is successful when the content matches the Receive String value. A TCP type of monitor takes a Send String value and a Receive String value. If the Send String value is blank and a connection can be made, the service is considered up. A blank Receive String value matches any response. Both Transparent and Reverse modes are options. For more information about Transparent and Reverse modes, see Using transparent and reverse modes .

The following list shows the settings for the pre-configured monitor tcp:

  • Name: tcp
  • Type: TCP
  • Interval: 30 seconds
  • Timeout: 120 seconds
  • Send String: "" (empty)
  • Receive String: "" (empty)
  • Reverse: No
  • Transparent: No
  • Alias Address: * All Addresses
  • Alias Service Port: * All Ports

HTTP

You can use an HTTP type of monitor to check the status of Hypertext Transfer Protocol (HTTP) traffic. Like a TCP monitor, an HTTP monitor attempts to receive specific content from a web page, and unlike a TCP monitor, may send a user name and password. The check is successful when the content matches the Receive String value. An HTTP monitor uses a send string, a receive string, a user name, a password, and optional Reverse and Transparent modes. (If there is no password security, you must use blank strings [""] for the Username and Password settings.)

For more information on transparent and reverse modes, see Using transparent and reverse modes .

The following list shows the settings of the pre-configured monitor http:

  • Name: http
  • Type: HTTP
  • Interval: 30 seconds
  • Timeout: 120 seconds
  • Send String: Get /
  • Receive String: "" (empty)
  • User Name: "" (empty)
  • Password: "" (empty)
  • Reverse: No
  • Transparent: No
  • Alias Address: * All Addresses
  • Alias Service Port: * All Ports

HTTPS

You use an HTTPS type of monitor to check the status of Hypertext Transfer Protocol Secure (HTTPS) traffic. An HTTPS type of monitor attempts to receive specific content from a web page protected by SSL security. The check is successful when the content matches the Receive String value.

HTTPS-type monitors use a send string, a receive string, a user name, a password, and an optional Reverse setting. (If there is no password security, you must use blank strings [""] for the Username and Password settings.) For more information on the Reverse setting, see Using transparent and reverse modes .

HTTP-type monitors also include the settings Cipher List, Compatibility, and Client Certificate. If you do not specify a cipher list, the monitor uses the default cipher list DEFAULT:+SHA:+3DES:+kEDH. When you set the Compatibility setting to Enabled, this sets the SSL options to ALL. You use the Client Certificate setting to specify a certificate file that the monitor then presents to the server.

The following list shows the settings of the pre-configured monitor https:

  • Name: https
  • Type: HTTPS
  • Interval: 30 seconds
  • Timeout: 120 seconds
  • Send String: Get /
  • Receive String: "" (empty)
  • Cipher List: "" (empty)
  • User Name: "" (empty)
  • Password: "" (empty)
  • Compatibility: Enabled
  • Client Certificate: "" (empty)
  • Reverse: No
  • Alias Address: * All Addresses
  • Alias Service Port: * All Ports

The Reverse mode is an option for monitors that import settings from the https monitor. For more information on Reverse mode, see Using transparent and reverse modes .

FTP Monitor

Using an FTP type of monitor, you can monitor File Transfer Protocol (FTP) traffic. A monitor of this type attempts to download a specified file to the /var/tmp directory, and if the file is retrieved, the check is successful.

Note

Once the file has been successfully downloaded, the GTM system does not save it.

An FTP monitor specifies a user name, a password, and a full path to the file to be downloaded.

The following list shows the settings and default values of an FTP-type monitor:

  • Name: my_ftp
  • Type: FTP
  • Interval: 10 seconds
  • Timeout: 31 seconds
  • User Name: "" (empty)
  • Password: "" (empty)
  • Path/Filename: "" (empty)
  • Mode: Passive
  • Alias Addresses: * All Addresses
  • Alias Service Port: * All Ports
  • Debug: No

Special configuration considerations

Every pre-configured or custom monitor has settings with some default values assigned. The following sections contain information that is useful when changing these default values.

Setting destinations

By default, the value for the Alias Address setting for most monitors is set to the wildcard * Addresses, and the Alias Service Port setting is set to the wildcard * Ports (exceptions to this rule are the WMI and Real Server monitors). This value causes the monitor instance created for a pool or virtual server to take that resource's address or address and port as its destination. You can, however, replace either or both wildcard symbols with an explicit destination value, by creating a custom monitor. An explicit value for the Alias Address and/or Alias Service Port setting is used to force the instance destination to a specific address and/or port which may not be that of the pool or virtual server.

The ECV monitors http, https, and tcp have the settings Send String and Receive String for the send string and receive expression, respectively.

The most common Send String value is GET /, which retrieves a default HTML page for a web site. To retrieve a specific page from a web site, you can enter a Send String value that is a fully qualified path name:

"GET /www/support/customer_info_form.html"

The Receive String expression is the text string the monitor looks for in the returned resource. The most common Receive String expressions contain a text string that is included in a particular HTML page on your site. The text string can be regular text, HTML tags, or image names.

The sample Receive expression below searches for a standard HTML tag:

"<HEAD>"

You can also use the default null Receive String value [""]. In this case, any content retrieved is considered a match. If both the Send String and Receive String are left empty, only a simple connection check is performed.

For HTTP and FTP monitors, you can use the special settings get or hurl in place of Send String and Receive String statements. For FTP monitors specifically, the GET setting specifies the full path to the file to retrieve.

Using transparent and reverse modes

The normal and default behavior for a monitor is to ping the destination pool or virtual server by an unspecified route, and to mark the resource up if the test is successful. However, with certain monitor types, you can specify a route through which the monitor pings the destination server. You configure this by specifying the Transparent or Reverse setting within a custom monitor.

  • Transparent setting
    Sometimes it is necessary to ping the destination through a transparent pool or virtual server. When you create a custom monitor and set the Transparent setting to Yes, the Link Controller forces the monitor to ping through the pool or virtual server with which it is associated (usually a firewall) to the pool or virtual server. (In other words, if there are two firewalls in a load balancing pool, the destination pool or virtual server is always pinged through the pool or virtual server specified and not through the pool or virtual server selected by the load balancing method.) In this way, the transparent pool or virtual server is tested: if there is no response, the transparent pool or virtual server is marked as down.
  • Common examples are checking a router, or checking a mail or FTP server through a firewall. For example, you might want to check the router address 10.10.10.53:80 through a transparent firewall 10.10.10.101:80. To do this, you create a monitor called http_trans in which you specify 10.10.10.53:80 as the monitor destination address, and set the Transparent setting to Yes. Then you associate the monitor http_trans with the transparent firewall (10.10.10.101:80).

    This causes the monitor to check the address 10.10.10 53:80 through 10.10.10.101:80. (In other words, the Link Controller routes the check of 10.10.10.53:80 through 10.10.10.101:80.) If the correct response is not received from 10.10.10.53:80, then 10.10.10.101:80 is marked down. For more information on associating monitors with virtual servers, see Associating monitors with resources .

  • Reverse setting
    With the Reverse setting set to Yes, the monitor marks the pool or virtual server down when the test is successful. For example, if the content on your web site home page is dynamic and changes frequently, you may want to set up a reverse ECV service check that looks for the string "Error". A match for this string means that the web server was down.

Figure 8.2 shows the monitors that contain the Transparent setting, the Reverse setting, or both.

Table 8.2 Monitors that contain the Transparent or Reverse settings
Monitor Type
Setting
TCP
Transparent
Reverse
HTTP
Transparent
Reverse
HTTP
 
Reverse
TCP Echo
Transparent
 
ICMP
Transparent
 

Associating monitors with resources

Once you have created a monitor and configured its settings, the final task is to associate the monitor with the resources to be monitored. The resources can be either a pool or virtual server, depending on the monitor type.

Some monitor types are designed for association with virtual servers only, and not pools. Other monitor types are intended for association with pools only, and not virtual servers. Therefore, when you use the Configuration utility to associate a monitor with a pool or virtual server, the utility displays only those pre-configured monitors that are designed for association with that server. For example, you cannot associate the monitor icmp with a pool, since the icmp monitor is designed to check the status of a virtual server itself and not any service running on that resource.

When you associate a monitor with a server, the Link Controller automatically creates an instance of that monitor for that server. A monitor association thus creates an instance of a monitor for each server that you specify. Therefore, you can have multiple instances of the same monitor running on your servers.

The Configuration utility allows you to disable an instance of a monitor that is running on a server. This allows you to suspend health or performance checking, without having to actually remove the monitor association. When you are ready to begin monitoring that server again, you simply re-enable that instance of the monitor.

Types of monitor associations

The types of monitor associations are:

  • Monitor-to-pool association
    This type of association links a monitor with an entire load balancing pool. In this case, the monitor checks all members of the pool. For example, you can create an instance of the monitor http for the pool my_pool, thus ensuring that all members of that pool are checked.
  • Monitor-to-pool member association
    This type of association links a monitor with a pool member within a given pool. For example, you can create an instance of the monitor FTP for specific pools within the pool my_pool, ensuring that only specific pool members are verified as available through the FTP monitor.
  • Monitor-to-virtual server association
    This type of association links a monitor with a specific virtual server. In this case, the monitor checks only the virtual server itself, and not any services running on that virtual server. For example, you can create an instance of the monitor icmp for virtual server 10.10.10.10. In this case, the monitor checks the specific virtual server only, and not any services running on that virtual server.

Managing monitors

When managing existing monitors, you can display or delete them, or you can enable and disable an instance of a monitor. Note that prior to deleting a monitor, you must remove all existing monitor associations.

To display a monitor

  1. On the Main tab of the navigation pane, expand Link Controller and then click Monitors.
    The monitors screen opens.
  2. Click a monitor name.
    The Properties screen of the monitor opens.

To delete a monitor

  1. On the Main tab of the navigation pane, expand Link Controller and then click Monitors.
    The monitors screen opens.
  2. Click the Select box for the monitor that you want to delete.
  3. Click the Delete button.
    A confirmation message appears.
  4. Click the Delete button.

To enable or disable a monitor instance

  1. On the Main tab of the navigation pane, expand Link Controller and then click Monitors.
    The monitors screen opens.
  2. Click a monitor name in the list.
  3. On the menu bar, click Instances.
    This lists any existing monitor instances.
  4. For the instance you want to manage, click the Select box.
  5. Click either the Enable or Disable buttons.
  6. Click the Update button to save your changes.



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