Jinja Syntax and Examples for Configuration Templates

Jinja Syntax and CSO Keywords

The tables below list the Jinja syntax used commonly in configuration templates and the keywords used in configuration templates respectively.

{{tenant_name}}

{# This is an example of comment in Jinja syntax #}

{% for prefix in Trusted_Network_Prefix_List %}
set groups trusted‐prefix policy‐options prefix‐list re‐ssh {{prefix.Trusted_Network_Prefix_List}}
{% endfor %}

Example 1: Convert a Single Junos OS Command to Jinja Syntax

If you want to convert a single Junos OS command into Jinja syntax for use in a configuration template:

1. Identify the variables that are configured in the Junos OS command.

   For example, in the command set snmp trap-group CSO-Trp-Grp targets 192.0.2.100, the variables configured are CSO-Trp-Grp and 192.0.2.100.

2. Convert the Junos OS CLI command to Jinja syntax by enclosing each variable in double curly braces as follows: {{ Variable_Name }}.

   So, in this example, if we use Trap_Group_Name and SNMP_Host_IP_Address as the variable names, the Jinja syntax for the command is as follows:

3. If you paste this in the Template Configuration section of the Add Configuration Template workflow, CSO detects the parameters as follows:

   Parameters

4. If you use the preview feature to render the configuration (for an OpCo named Juniper and a configuration template named Test), using the values indicated in the first step, CSO renders the configuration as follows:

   Notice that although you provided the JInja syntax for a single Junos OS command, CSO added additional commands to the configuration. This is because, by default, CSO uses Junos OS groups to generate the configuration. Junos OS groups make it easier to apply and delete configurations. For more information, see Understanding Junos OS Configuration Groups.

   If you don’t want to use Junos OS groups, you must turn on the advanced mode in the configuration template, when you specify the configuration in Jinja syntax..

Example 2: Convert a Junos OS Configuration Snippet to Jinja Syntax

In this example, we’ll convert the following Junos OS configuration snippet into Jinja syntax for use in a configuration template:

To convert the Junos OS configuration into Jinja syntax:

1. Identify the variables that are configured in the Junos OS commands. For ease of understanding, the variables are enclosed within angular brackets (<>) in the example below.

   Note:

   In this example, we’re not considering DHCP-SERVER as a variable.

2. Convert each Junos OS CLI command to Jinja syntax by identifying the variables, providing a name for each variable, and enclosing each variable in double curly braces. So, in this case, the Jinja syntax is as follows:

3. When you paste this in the Template Configuration section of the Add Configuration Template workflow, CSO detects the parameters as follows:

   Parameters

4. If you use the preview feature to render the configuration (for an OpCo named Juniper and a configuration template named Test), using the values for this example, CSO renders the configuration as follows:

Example 3: Use Conditional Logic

In this example, which is a modified version of the preceding example, we’ll see how you can use conditional logic (if and for statements) in a configuration template.

The explanation of the example above is as follows:

1. In this example, we add an if statement and enclose the configuration within that statement as follows:

   This means that the configuration is applied only if the enable_Forwarding_Options is True. If enable_Forwarding_Options is False, then no configuration is applied.

   Tip:

   If you want to apply a different configuration when enable_Forwarding_Options is False, you can use the else statement.

2. Then, we add a for statement to enable the configuration of more than one set of values for the Relay_Group_Name, Relay_Interface, and Relay_Zone variables.

   When you use a for statement, the GUI rendered by CSO (when you use the preview feature) displays the variables in table (grid). You can then use the Add icon (+) to add rows to the table and configure one or more sets of values as needed.

3. When you paste the Jinja commands in the Template Configuration section of the Add Configuration Template workflow, CSO detects the parameters as follows:

   Parameters

4. If you use the preview feature to render the configuration (for an OpCo named Juniper and a configuration template named Test), and provide values for the parameters, including two sets of values for Relay_Group_Name, Relay_Interface, and Relay_Zone, CSO renders the configuration as follows:

Example 4: Use Variable Substitution

In this example, we use a variable as part of the configuration command such that the value that we specify for the variable is used in the command.

The explanation of the example above is as follows:

1. We use the VLAN_Id attribute of the pool parameter to set the Junos OS configuration parameters vlans and vlan-id.

2. When you paste the Jinja command set groups MIST vlans V-{{pool.VLAN_Id}} vlan-id {{pool.VLAN_Id}} in the Template Configuration section of the Add Configuration Template workflow, CSO detects the parameters as follows:

   Parameters

   This is because we’ve used the dot (.) operator to reference the attribute VLAN_Id of the parameter pool.

3. If you use the preview feature to render the configuration (for an OpCo named Juniper and a configuration template named Test), and provide the value 120 for VLAN_Id, CSO renders the configuration as follows:

   In the rendered configuration command, you can see that the parameters vlans and vlan-id are set to V-120 and 120 respectively, based on the value that we provided for the VLAN_Id parameter.

Example 5: Use Filters, Concatenation, and Set Variables

In this example, we’ll look at how to set a variable using concatenation and filters, and then use that variable in a Junos OS configuration command.

The explanation of the example above is as follows:

1. The Jinja statement {% set pool_name = Dhcp_Server_Name + ’_’ + Interface | replace(“/”,”_”) %} is used to set a variable called pool_name, using two other variables Dhcp_Server_Name and Interface, as follows:

   1. The | (pipe) operator is used to separate variables from filters, which are functions that modify variables. In this example, we use the replace(“/”,”_”) filter to modify the Interface variable by replacing the / (forward slash) characters with _ (underscore) characters.

   2. Then, we use the + operator to concatenate the resulting string with the variable Dhcp_Server_Name.

      Note:

      The operator + is typically used to add numbers, but when the values are strings, the strings are concatenated.

   3. Finally, the tag set is used (along with the = operator) to set the variable called pool_name to the concatenated variable.

2. Then, the Junos OS command set system services dhcp-local-server overrides process-inform pool {{pool_name}} is used to configure the Junos OS configuration statement pool using the variable pool_name that we set in the preceding step.

3. When you paste the Jinja commands in the Template Configuration section of the Add Configuration Template workflow, CSO detects the parameters as follows:

   Parameters

   As you can see, the Junos OS command or the pool_name variables are not displayed because we’re using the Interface and Dhcp_Server_Name variables to arrive at the final Junos OS configuration.

4. If you use the preview feature to render the configuration (for an OpCo named Juniper and a configuration template named Test), and provide the values LA_dhcp_srvr for Dhcp_Server_Name and ge-0/1/2 for the Interface, CSO renders the configuration as follows:

   As explained in a previous step, the / characters in ge-0/1/2 are first replaced with _ characters, which changes the string to ge-0_1_2. This string is concatenated with LA_dhcp_srvr to produce the string LA_dhcp_srvr_ge-0_1_2, which is used in the Junos OS configuration command.

   Therefore, the Junos OS configuration command generated is set system services dhcp-local-server overrides process-inform pool LA_dhcp_srvr_ge-0_1_2.

Example 6: Test a Value

In this example, we’ll look at how to test a value and perform actions based on the result of the test conditions.

The explanation of the example above is as follows:

1. We test the parameter NewNetwork.VLAN_Id for two conditions:

   1. Whether the parameter is defined (by using the NewNetwork.VLAN_Id is defined condition)

   2. Whether the length of the parameter is greater than two (by using the condition (NewNetwork.VLAN_Id | count) > 2)

   Because we use the keyword and:

   • The configuration command set vlan-id {{NewNetwork.VLAN_Id}} is added to the configuration (that CSO generates) when both conditions hold true.

   • The configuration set vlans VL-{{NewNetwork.VLAN_Id}} is added to the configuration when either of the conditions is false.

2. When you paste the Jinja commands in the Template Configuration section of the Add Configuration Template workflow, CSO detects the parameters as follows:

   Parameters

3. If you use the preview feature to render the configuration (for an OpCo named Juniper and a configuration template named Test), and:

   • Provide the value 125 for VLAN_Id, CSO renders the configuration as follows because both conditions are true:

   • Provide the value 65 for VLAN_Id, CSO renders the configuration as follows because one of the conditions is false (length of the parameter is not greater than 2):