Reason for Blank Output

C

You must add the mpls configuration within the [edit protocols mpls] hierarchy.

Example:

Configure -

set protocols mpls interface ge-1/1/0.0

commit and-quit

The "show mpls interface" command is used to display the status of all MPLS interfaces and associated label-switched paths (LSPs) on the router. If the output of this command is blank, it indicates that no MPLS interfaces or LSPs have been configured on the router.

Based on the given options, we can eliminate option A as it pertains to the authentication configuration of the interface, which is not related to MPLS.

Option B, "family mpls" not being configured on the logical interface, is a possible reason for the blank output. The "family mpls" statement is required on the logical interface to enable MPLS forwarding. If it is not configured, the router will not be able to forward MPLS packets and will not have any MPLS interfaces to display with the "show mpls interface" command.

Option C, "no configuration was added to the [edit protocols mpls] hierarchy," is another possible reason for the blank output. The [edit protocols mpls] hierarchy is used to configure MPLS on the router, including configuring MPLS interfaces and LSPs. If no configuration has been added to this hierarchy, there will be no MPLS interfaces or LSPs to display with the "show mpls interface" command.

Finally, option D, "no configuration was added to the [edit protocol rsvp] hierarchy," is also a possible reason for the blank output. RSVP is the protocol used to set up and maintain MPLS LSPs. If no configuration has been added to the [edit protocols rsvp] hierarchy, there will be no LSPs to display with the "show mpls interface" command.

In summary, options B, C, and D are all possible reasons for the blank output of the "show mpls interface" command, but without additional information about the router configuration, it is impossible to determine the exact reason for the issue.