3

Configuring Nodes

Introducing nodes

Nodes are the network devices to which a BIG-IP^® local traffic management system passes traffic. You can explicitly create a node, or you can instruct the BIG-IP 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 BIG-IP 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 BIG-IP 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

To modify an existing node

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.

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.

Assigning health monitors

Using the BIG-IP system, you can monitor the health or performance of your nodes by associating 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 BIG-IP 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. That is, the destination address in the monitor specifies an IP address only, rather than an IP address and a service port.

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

For more information about health and performance monitors, see Chapter 12, Configuring Monitors .

Specifying a default monitor

As explained earlier in this chapter, if you create a pool member without first creating the parent node, the BIG-IP system automatically creates the parent node for you. Fortunately, you can configure the BIG-IP system to automatically associate one or more monitor types with every node that the BIG-IP system creates. This eliminates the task of having to explicitly choose monitors for each node.

To associate one or more monitors with every node by default, you must first specify the monitors that you want to assign to nodes (see To specify one or more default monitors , following). Once you have performed this task, the BIG-IP system then assigns the specified default monitors to any node that the system automatically creates.

To specify one or more default monitors

Explicitly associating monitors with a node

Sometimes, you might want to explicitly create a node, rather than having the BIG-IP system create the node automatically. In this case, when you create the node and configure its Health Monitors setting, you can either:

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 BIG-IP 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. Using the Configuration utility, you can:

Viewing a list of nodes

You can view a list of the existing nodes. When you display the list of nodes, the Configuration utility displays the following information about each node:

Use the following procedure to view a list of nodes defined on the BIG-IP system.

To view the list of nodes

On the Main tab, expand Local Traffic, and click Nodes.
This opens the Nodes screen and displays a list of nodes.

Viewing node properties

You can use the Configuration utility to view the general properties of a node. These properties and their descriptions are:

To view node properties

Understanding node status

At any time, you can determine the status of a node, using the Configuration utility. You can find this information by displaying the list of nodes and viewing the Status column, or by viewing the Availability property of a node.

The Configuration utility indicates status by displaying one of several icons, distinguished by shape and color:

To understand these icons with respect to node status, see Table 3.2 . To display the icons within the Configuration utility, see To view node properties .

Table 3.2 Explanation of status icons for nodes

Status indicator	Explanation
	The node is enabled and able to receive traffic.
	The node is enabled but is currently unavailable. However, the node might become available later, with no user action required. An example of an unavailable node becoming available automatically is when the number of concurrent connections to the node no longer exceeds the value defined in the node's Connection Limit setting.
	The node is enabled but offline because an associated monitor has marked the node as down. To change the status so that the node can receive traffic, user intervention is required.
	The node is set to Disabled, although a monitor has marked the node as up. To resume normal operation, you must manually enable the node.
	The node is set to Disabled and is down. To resume normal operation, you must manually enable the node
	The node is set to Disabled and is offline either because a user disabled it, or a monitor has marked the node as down. To resume normal operation, you must manually enable the node.
	The status of the node is unknown. Sample reasons for unknown node status are: The node has no monitor associated with it. Monitor results are not available yet. The node's IP address is misconfigured. The node has been disconnected from the network.

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Enabling or disabling a node

A node must be enabled in order to accept traffic. When a node is disabled, the BIG-IP 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

Deleting a node

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

To delete a node

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 remove any default monitors, that is, monitors that the BIG-IP system automatically associates with any node that you create.

For more information on monitor associations, see Assigning health monitors .

To remove an explicit monitor association for a node

To remove a default monitor