You can set a default Jira server for all GitLab projects ([see external issue tracker document](external-issue-tracker.md#service-template)) but you can also configure a project to connect to another Jira server than the default one.
Once the project is connected to Jira, you can reference and close the issues in Jira directly from GitLab.
Each project can be configured to connect to a different Jira instance, configuration is explained [here](#configuration).
If you have one Jira instance you can pre-fill the settings page with a default template. To configure the template [see external issue tracker document](external-issue-tracker.md#service-template)).
Once the project is connected to Jira, you can reference and close the issues in Jira directly from GitLab. This functionality is only available in GitLab Enterprise Edition as described in this document.