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Expanding the Custom Syntax

In the corresponding commit script, you include one or more XSLT or SLAX programming instructions that inspect the configuration for the apply-macro statement at a specified hierarchy level. Optionally, you can use the data/name expression to select a parameter in the apply-macro statement:



<xsl:for-each select="xpath-expression/apply-macro[data/name = 'parameter-name']">

For example, the following XSLT programming instruction selects every apply-macro statement that contains the color parameter and that appears at the [edit protocols mpls] hierarchy level:



<xsl:for-each select="protocols/mpls/apply-macro[data/name
= 'color']">

In SLAX, the syntax looks like this:



for-each (protocols/mpls/apply-macro[data/name = 'color'])

When expanding macros, a particularly useful programming instruction is the <xsl:value-of> instruction. This instruction selects a parameter value and uses it to build option values for JUNOS statements. For example, the following instruction concatenates the value of the $color variable, the text -lsp-, and the current context node (represented by “ .” ) to build a name for an LSP.



<label-switched-path>
    <name> 
        <xsl:value-of select="concat($color, '-lsp-', .)"/>
    </name>
</label-switched-path>

In SLAX, the syntax uses the underscore (_) to concatenate values:



<label-switched-path> {
    <name> $color _  '-lsp-' _  .;

Now that you have provided the script with instructions to find the necessary data, you can provide content for a transient change that uses the data to construct a standard JUNOS configuration.

The following transient change creates an administration group and adds the label-switched-path statement to the configuration. The label-switched path is assigned a name that concatenates the value of the $color variable, the text -lsp-, and the currently selected IP address represented by the “ .” . The transient change also adds the to statement and assigns the currently selected IP address. Finally, the transient change adds the admin-group include-any statement and assigns the value of the $color variable.



<transient-change>
    <protocols>
        <mpls>
            <admin-groups>
                <name><xsl:value-of select="$color"/></name>
                <group-value><xsl:value-of select="$group-value"/></group-value>
            </admin-groups>
            <xsl:for-each select="data[not(value)]/name">
                <label-switched-path>
                    <name><xsl:value-of select="concat($color, '-lsp-', .)"/></name>
                    <to><xsl:value-of select="."/></to>
                    <admin-group>
                        <include-any><xsl:value-of select="$color"/></include-any>
                    </admin-group>
                </label-switched-path>
            </xsl:for-each>
        </mpls>
    </protocols>
</transient-change>

In SLAX, the syntax looks like this:



<transient-change> {
    <protocols> {
        <mpls> {
            <admin-groups> {
                <name> $color;
                <group-value> $group-value;
            }
            for-each (data[not(value)]/name) {
                <label-switched-path> {
                    <name> $color _  '-lsp-' _  .;
                    <to> .;
                    <admin-group> {
                        <include-any> $color;
                    }
                }
            }
        }
    }
}

Note: The example shown here is partial. For a full example, see Example: Creating Custom Configuration Syntax with Macros.

After committing the configuration, the script runs, and the resulting full configuration looks like this:



protocols {
    mpls {
        label-switched-path blue-lsp-10.1.1.1 {
            to 10.1.1.1;
            admin-group include-any blue;
        }
        label-switched-path blue-lsp-10.2.2.2 {
            to 10.2.2.2;
            admin-group include-any blue;
        }
        label-switched-path blue-lsp-10.3.3.3 {
            to 10.3.3.3;
            admin-group include-any blue;
        }
        label-switched-path blue-lsp-10.4.4.4 {
            to 10.4.4.4;
            admin-group include-any blue;
        }
    }
}

The previous example demonstrates how you can use a simplified custom syntax to configure label-switched paths (LSPs). If your network design requires a large number of LSPs to be configured, using a commit script macro can save time, ensure consistency, and prevent configuration errors.

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