You want to check the syntax of your configuration to make sure there are no errors or missing statements.
Check the syntax of the configuration:
 aviva@router1# commit check configuration check succeeds  aviva@router1#
As you are configuring the router, if you mistype a JUNOS configuration statement or command, the CLI gives you immediate feedback and pesters you until you type it correctly. However, this does not guarantee that you have spelled all variable names correctly or that you haven't omitted any required statements. Use the commit check command from time to time to check the syntax of the configuration. This command only checks the syntax; it does not activate the configuration.
If the syntax has no errors, you see the message configuration check succeeds.
If you have made any mistakes in the configuration, a message reports where in the configuration hierarchy the mistake is and describes the problem. The following example shows that a RIP neighbor router has been incorrectly configured in two RIP groups:
 aviva@router1# commit check [edit protocols rip group alpha-rip-group] 'neighbor fe-0/0/0.0' Failed to configure neighbor fe-0/0/0.0: already in group alpha-rip-group error: configuration check-out failed
This is a mistake because a RIP neighbor can be in only one group. You can see from the output that the mistake is at the [edit protocols rip group alpha-rip-group] hierarchy level of the configuration.
Even if the syntax of the configuration is correct, that is no guarantee that the configuration will work as expected.
Router Configuration and File Management
Basic Router Security and Access Control
Routing Policy and Firewall Filters