Describe Nodes

• To add a node group with the Describe Nodes option:

1. Click the Select Nodes tab.
2. Click the Add New Row icon to add a row in the table for a new rule. Rules take the form of an expression which can be compared against nodes.
3. Double-click each column in the row to turn the appropriate cell into a drop-down menu, then select the appropriate value for each component:
   • Prefix - Leave this blank or select NOT. If NOT is selected, this rule will filter for values opposite of the rest of the expression.
   • Category - Select an attribute that will be evaluated in the rule. All categories you created in the Association Manager will be available here. Also included are Node Name and Interface. If any blade chassis has been configured in the system, a Blade Chassis category is available by default.
   • Operator - Select a comparison operation to be performed between the Category and Element items. Three operators are available: = (is equal to), LIKE (used for find the Element in a name) and <> (is not equal to).
   • Element - Select a value for the Category attribute to be compared against. Only elements associated with the selected category will appear here (for example: if evaluating a “Department” category, “Location” elements will not appear here).
   • Rule Name- This is a name assigned to the rule in this row. You cannot edit these values. Use these values for writing descriptions in the Short Expression field.

     An example rule might be Department = Engineering, meaning it describes all nodes that the category “Department” set to “Engineering.” This is exactly what happens when you configure the associations during an Add Node operation.

4. If you want to add another rule, click the Add New Row icon again, and make the necessary configurations. Configuring multiple rules will allow more precise descriptions by providing multiple criteria for evaluating nodes.
   • To remove a rule, highlight the rule in the table, and then click the Remove Row icon .
5. The table of rules makes available criteria for evaluating nodes. To write a description for the node group, add the rules by Rule Name to the Short Expression field. If the description only requires a single rule, then type that rule's name in the field. If multiple rules are being evaluated, type the rules into the field using a set of logical operators to describe the rules in relation to each other:
   • & - the AND operator. A node must satisfy rules on both sides of this operator for the description (or that section of a description) to be evaluated as true.
   • | - the OR operator. A node only needs to satisfy one rule on either side of this operator for the description (or that section of a description) to be evaluated as true.
   • ( and ) - grouping operators. This breaks the description into a subsection contained within the parentheses. The section within the parentheses is evaluated first before the rest of the description is compared to the node. Parenthetical groups can be nested inside another parenthetical group.

     Example 1: If you want to describe nodes that belong to the engineering department, create a rule that says Department = Engineering. This will become Rule0. Then, type Rule0 in the Short Expression field.

     Example 2: If you want to describe a group of devices that belong to the engineering department or are located in Philadelphia, and specify that all of the machines must have 1 GB of memory, you must create three rules. Department = Engineering (Rule0) Location = Philadelphia (Rule1) Memory = 1GB (Rule2).These rules must be arranged in relation to each other. Since the device can either belong to the engineering department or be located in Philadelphia, use the OR operator, |, to join the two: Rule0 | Rule1. Make this comparison first by enclosing it parentheses: (Rule0 | Rule1). Since the devices must both satisfy this comparison AND contain 1GB of memory, use the AND connector, &, to join this section with Rule2: (Rule0 | Rule1) & Rule2. Type this final expression in the Short Expression field.

     Note: You should have a space before and after operators & and |. Otherwise, the Short Expression field may return to the default expression, that is, Rule0 & Rule1 & Rule2 and so on, when you delete any rule from the table.

6. Click Validate when a description has been written in the Short Expression field. If the description is formed incorrectly, a warning appears. If the description is formed correctly, a normalized form of the expression appears in the Normalized Expression field.
7. Click View Nodes to see what nodes satisfy this expression. A Nodes in Node Group window opens, displaying the nodes that will be grouped by the current expression. This can be used to check if the description was correctly written. If not, you can return to the rules table or the Short Expression field to make adjustments.
8. If you know you want to create a policy that allows access to the nodes in this group at all times, select the Create Full Access Policy for Group checkbox.
9. When you are done describing the nodes that belong in this group, click OK to create the node group. The group will be added to the list of Node Groups on the left.