Multiprotocol Label Switching Checklist
This chapter provides a checklist to troubleshoot the Multiprotocol Label Switching (MPLS) protocol.
You can collect information from the sample output on all routers for the following commands to troubleshoot the problems in MPLS:
•show tech-support mpls rsvp
•show tech-support mpls traffic-eng
•show tech-support routing ospf
•show tech-support routing isis
For more detailed information about the show tech-support commands, see Cisco IOS XR Advanced System Command Reference for the Cisco CRS-1 Router.
Multiprotocol Label Switching Recommendations
Follow these recommendations to troubleshoot Multiprotocol Label Switching (MPLS):
•Verify the show commands for the MPLS control plane to ensure that there is no problem.
•Ensure that the hardware is programmed correctly for Multiprotocol Label Switching (MPLS) Traffic Engineering (TE) and Label Distribution Protocol (LDP).
•Ensure that there are no communication problems in the MPLS infrastructure. If the control plane has some problems, determine if they are due to the following reasons:
–Communication problems in the Resource Reservation Protocol (RSVP) infrastructure . In certain instances, the tunnel is not up though the topology is correct and the RSVP messages are lost.
–Communication problems with the MPLS-TE infrastructure .
•Verify the sample output from the applicable show tech-support commands on all routers in the entire network topology. Copy the output to the applicable TFTP location.
–For MPLS-TE issues, verify the output from the show tech-support mpls traffic-eng, show tech-support mpls rsvp, show tech-support routing ospf, and show tech-support routing isis commands.
–For MPLS LDP issues, verify the output from the show tech-support mpls ldp command.
•Provide a topology diagram that indicates the applicable platform.
•Specify the symptom of the problem. For example, for an MPLS-TE tunnel, the problem is detected at the head, middle, or tail of a tunnel.
•Determine how the problem state was encountered.
•Verify if the problem can be reproduced. If it can be reproduced, list the detailed steps to reproduce the problem.
•Provide a decoded stack trace and core file for a process crash. Copy the core file to the applicable TFTP location.
•Save the sample output from the show logging command to a file. Copy the file to the applicable TFTP location. For more information, see Cisco IOS XR System Monitoring Command Reference for the Cisco CRS-1 Router.
Troubleshooting L3VPN MPLS Traffic Loss
To troubleshoot the traffic loss of MPLS packets on L3VPN layer in Cisco CRS-1, perform the following procedure. The general flow of packets in a Cisco CRS-1 goes through the following sequence:
Incoming interface => Ingress pse (the forwarding asic or mircocode) => Ingress queuing asic(xbma) => Switch fabric => Egress pse(forwarding asic or microcode) => Egress queuing asic(xbma) => Outgoing interface.
For detailed steps, see Troubleshooting Transient Traffic Drop in Forwarding in the Troubleshooting Forwarding chapter.