On Junos platforms, when the MPLS (Multi-protocol Label Switching) packet reaches the destination router, it will have a label that is unknown to the destination router due to a label POP operation miss at the ingress router resulting in the traffic black hole in the scenario SR-MPLS (Segment Routing With Multi-protocol Label Switching) + traffic engineering shortcut is configured.
The traffic of any service that resolves over L-ISIS (Labeled ISIS) will be blackholed as the label operation was missing a label POP operation at the ingress router (where SRTE + shortcuts is configured).
This issue will be seen when the following configuration is present
'set protocols source-packet-routing source-routing-path <> use-for-shortcut'.
To check the issue, execute the CLI command:
root@router> show route label <label>
<label> *[L-ISIS/XX] <TIMESTAMP>, metric 10
> to XXX.XXX.XX.X via ge-0/0/1.0
to XXX.XXX.XX.X via ge-0/0/2.0, Push <label>
<label>(S=0) *[L-ISIS/XX] <TIMESTAMP>, metric 10
Add the below line on the tail-end LSR where the SRTE shortcut LSP terminates:
'set protocols isis source-packet-routing explicit-null'.
.