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Manual Chapter: BIG-IP version v9.0 Configuration Guide for Local Traffic Management: Configuring Nodes
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3

Configuring Nodes


Introducing nodes

Nodes are the network devices to which a BIG-IP® local traffic management (LTM) system passes traffic. You can explicitly create a node, or you can instruct the LTM system to automatically create one when you add a pool member to a load balancing pool.

The difference between a node and a pool member is that a node is designated by the device's IP address only (10.10.10.10), while designation of a pool member includes an IP address and a service (such as 10.10.10:80).

A primary feature of nodes is their association with health monitors. Like pool members, nodes can be associated with health monitors as a way to determine server status. However, a health monitor for a pool member reports the status of a service running on the device, whereas a health monitor associated with a node reports status of the device itself.

For example, if an ICMP health monitor is associated with node 10.10.10.10, which corresponds to pool member 10.10.10.10:80, and the monitor reports the node as being in a down state, then the monitor also reports the pool member as being down. Conversely, if the monitor reports the node as being in an up state, then the monitor reports the pool member as being either up or down, depending on the status of the service running on it.

You create a node using the Configuration utility, and then adjust the settings as needed. Using the same utility, you can also display information about nodes, enable and disable nodes, and delete nodes.

Creating and modifying nodes

Nodes are the basis for creating a load balancing pool. For any server that you want to be part of a load balancing pool, you must first create a node, that is, designate that server as a node. After designating the server as node, you can add the node to a pool as a pool member. You can also associate a health monitor with the node, to report the status of that server. For information on adding nodes to load balancing pools, see Chapter 4, Configuring Load Balancing Pools .

You use the Configuration utility to create a node. When you create a node, the LTM system automatically assigns a group of default settings to that node. You can retain these default settings or modify them. You can also modify the settings at a later time, after you have created the node. For information on these settings, see either Configuring node settings , or the online help.

It is helpful to understand that the LTM system designates some settings as basic and others as advanced. If you decide to modify some of the default settings when you create the node, be sure to select the Advanced option on the screen to view all configurable settings. For more information on basic and advanced settings, see Chapter 1, Introducing Local Traffic Management .

To create a node

  1. On the Main tab, expand Local Traffic.
  2. Click Nodes.
    The Nodes screen opens.
  3. In the upper-right corner of the screen, click Create.
    The New Node screen opens.
  4. For the Address setting, type the IP address of the node.
  5. Specify, retain, or change each of the other settings.
  6. Click Finished.

To modify an existing node

  1. On the Main tab, expand Local Traffic.
  2. Click Nodes.
    The Nodes screen opens.
  3. In the Address column, click an address.
    This displays the settings for that node.
  4. Retain or modify any node settings.
  5. Click Update.

Configuring node settings

You can configure node settings to tailor nodes to your specific needs. For those settings that have default values, you can retain those default settings or modify them. Also, you can modify settings either when you create the node, or at any time after you have created it.

Table 3.1 lists these configurable settings and their default values. Following this table are descriptions of specific settings.

Table 3.1 Node configuration settings
Node settings
Description
Default Value
Address
Specifies the IP address of the node. This setting is required.
No default value
Name
Specifies the name of the node.
No default value
Health Monitors
Associates a health or performance monitor with a node.
No default value
Select Monitors
Specifies the monitors that the LTM system is to associate with the node.
No default value
Availability Requirement
Specifies the minimum number of health monitors that must report a node as being available to receive traffic before the LTM system reports that node as being in an up state.
All
Ratio
Specifies the ratio weight you want to assign to the node.
1
Connection Limit
Specifies the maximum number of concurrent connections allowed on a node.
0

 

Before configuring a node, it is helpful to have a description of certain node settings that you might want to change.

Specifying an address for a node

For each node that you configure, you must specify an IP address. An example of a node IP address is 10.10.10.10. This is the only required setting.

Specifying a node name

For each node that you configure, you can give it a unique node name, such as Node_1. Node names are case-sensitive and may contain letters, numbers, and underscores (_) only. Reserved keywords are not allowed.

Specifying monitor associations

Using the LTM system, you can monitor the health of performance of your nodes by associating health or performance monitors with those nodes. This is similar to associating a monitor with a load balancing pool, except that in the case of nodes, you are monitoring the IP address, whereas with pools, you are monitoring the services that are active on the pool members.

The LTM system contains many different pre-configured monitors that you can associate with nodes, depending on the type of traffic you want to monitor. You can also create your own custom monitors and associate them with nodes. The only pre-configured monitors that are not available for associating with nodes are monitors that are specifically designed to monitor pools or pool members rather than nodes.

There are two ways that you can associate a monitor with a node, by assigning the same monitor to multiple nodes at the same time, or by explicitly associating a monitor with each node as you create it.

Note

If you use the bigpipe utility commands node and save to assign the same monitor to multiple nodes (for example, bigpipe node all monitor icmp and bigpipe save), the system creates a separate monitor-node entry in the bigip.conf file for each node.

For more information on health and performance monitors, see Chapter 10, Configuring Monitors .

Creating a default monitor association

You can configure the LTM system to automatically associate one or more monitor types with every node that you create. In this case, you choose the monitors before you create your nodes, and then by default, the LTM associates those monitors with every node that you create. This eliminates the task of having to explicitly associate monitors with each node that you create.

You designate the default monitor for your nodes by navigating to the Nodes page and using the Default Monitor menu. Then when you create your node, you can set the value of the Health Monitors setting to Node Default.

Note

If you want to assign a default monitor to an existing node, you can use the same Default Monitor menu to do this.

Explicitly associating monitors with a node

Instead of configuring the LTM system to automatically associate one or more monitors with every node that you create, you can associate specific monitors with a node when you create that node.

You associate a monitor to a specific node (instead of all nodes as in the case of default monitor associations) by setting the value of the Health Monitors setting to Node Specific when you create a node or modify a node's settings. The Configuration utility then allows you to choose from a list of monitors that are available for associating with that node.

Specifying the availability requirement

By configuring the Availability Requirement setting, you can specify the minimum number of health monitors that must report a node as being available to receive traffic before the LTM system reports that node as being in an up state. Acceptable values are All or a number that you specify. If you choose the value At Least, you then specify a number.

Specifying a ratio weight

The Ratio setting specifies a ratio weight for the node. The default setting is 1. For information on ratio weights, see Chapter 4, Configuring Load Balancing Pools .

Setting a connection limit

Using the Connection Limit setting, you can specify the maximum number of concurrent connections allowed for a node. Note that the default value of 0 (zero) means that there is no limit to the number of concurrent connections that the node can receive.

Managing nodes

After you have created your nodes and configured their settings to suit your needs, you might want to perform some additional management tasks. You can manage existing nodes in these ways:

  • Viewing existing nodes
  • Enabling or disabling existing nodes
  • Deleting existing nodes
  • Disabling monitor associations
  • Displaying node status

Viewing existing nodes

You can use the following procedure to view nodes that you have created.

To view existing nodes

  1. On the Main tab, expand Local Traffic.
  2. Click Nodes.
    This displays a list of existing nodes.
  3. In the Address column, click the address of the node you want to view.
    This displays the settings for that node.

Enabling and disabling a node

A node must be enabled in order to accept traffic. When a node is disabled, the LTM system allows existing connections to time out or end normally. In this case, the node can accept new connections only if the connections belong to an existing persistence session. (In this way a disabled node differs from a node that is set to down. The down node allows existing connections to time out, but accepts no new connections.)

To enable or disable a node

  1. On the Main tab, expand Local Traffic.
  2. Click Nodes.
    This displays a list of existing nodes.
  3. Locate the address of the node you want to enable or disable.
  4. In the column to the left, check the Select box.
  5. At the bottom of the screen, click the Enable or Disable button.

Deleting a node

If you are no longer using a node in a pool, you can delete the node.

To delete a node

  1. On the Main tab, expand Local Traffic.
  2. Click Nodes.
    This displays a list of existing nodes.
  3. Locate the address of the node you want to enable or disable.
  4. In the column to the left, check the Select box.
  5. On the bottom of the screen, click Delete.
    A confirmation screen appears.
  6. Click Delete.

Removing monitor associations

Using the Configuration utility, you can remove a monitor that is explicitly associated with a specific node. When removing a monitor associated with a specific node, you can either remove the monitor association altogether, or change it so that only the default monitor is associated with the node.

Alternatively, you can also remove any default monitors, that is, monitors that the LTM system automatically associates with any node that you create.

For more information on monitor associations, see Specifying monitor associations .

To remove an explicit monitor association for a node

  1. On the Main tab, expand Local Traffic.
  2. Click Nodes.
    This displays a list of existing nodes.
  3. Click the address of the node you want to manage.
  4. In the Configuration section of the screen, locate the Health Monitors setting.
  5. Select Node Default or None.
  6. Click Update.

To remove a default monitor

  1. On the Main tab, expand Local Traffic.
  2. Click Nodes.
    This displays a list of existing nodes.
  3. Click the Default Monitor menu.
  4. Using the right arrows (>>), move any active monitors from the Active box to the Available box.
  5. Click Update.

Displaying node status

The Nodes screen automatically displays the status of all existing nodes. Available status values are:

  • All
  • Available
  • Unavailable
  • Offline
  • Unknown



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