Cisco IOS XR Troubleshooting Guide for the Cisco ASR 9000 Aggregation Services Router
Troubleshooting MPLS
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Troubleshooting MPLS Services

Table Of Contents

Troubleshooting MPLS Services

Verifying MPLS PIE Activation and MPLS Configuration

Troubleshooting Connectivity Over MPLS

Using show and debug Commands

IP Packets Not Forwarded to LSP

IP Packets Not Forwarded to MPLS TE Tunnel

MPLS Packets Not Forwarded to MPLS TE Tunnel

MPLS TE Tunnels Do Not Come Up

FRR-Protected Tunnel Goes Down After Triggering FRR

MPLS TE FRR Database Not Built

MPLS FRR Switch Time Debugging


Troubleshooting MPLS Services


This chapter describes techniques to troubleshoot MultiProtocol Label Switching (MPLS) services. MPLS carries different kinds of traffic, such as IP packets and Ethernet frames. The general flow of packets in a Cisco ASR 9000 Aggregation Series Router is as follows:

Incoming interface => Ingress NP => Switch fabric => Egress NP => Outgoing interface.

This chapter contains the following subsections:

Verifying MPLS PIE Activation and MPLS Configuration

Troubleshooting Connectivity Over MPLS

Using show and debug Commands

IP Packets Not Forwarded to LSP

IP Packets Not Forwarded to MPLS TE Tunnel

MPLS Packets Not Forwarded to MPLS TE Tunnel

MPLS TE Tunnels Do Not Come Up

FRR-Protected Tunnel Goes Down After Triggering FRR

MPLS TE FRR Database Not Built

MPLS FRR Switch Time Debugging

Verifying MPLS PIE Activation and MPLS Configuration

For operation of MPLS, the MPLS PIE must be active and MPLS must be present in your running configuration:

Verify that the MPLS PIE is installed, committed, and activated. It is not installed by default.

Verify that MPLS is configured in your running-config. After you install the MPLS PIE, you must commit it. If you configure MPLS but you have not committed the MPLS PIE, the system deletes all of your MPLS configuration if you reload the router image.


Caution Verify that the MPLS PIE is committed before you configure MPLS. Otherwise all of your MPLS configuration data will be lost if the image is reloaded.

Troubleshooting Connectivity Over MPLS

This section explains how to troubleshoot MPLS connectivity for multipoint Layer 2 services.


Step 1 Ping the opposite interface (on the remote router) on the MPLS interface. Verify that the ping is successful.

Step 2 Verify that the remote interface shows up as an ospf neighbor.

show ospf neigbor
 
   

Step 3 Verify that the remote router ID (typically the remote router loopback) is in the routing table.

show route ipv4
 
   

Step 4 Ping the IP address of the remote router (the same IP address that was displayed in Step 3). Verify that the ping is successful.

Step 5 Verify that label distribution protocol (LDP) is up between the local and remote routers.

show mpls ldp neighbor

Step 6 Verify that you can find the ID of the remote router in an MPLS command. In the case of a PW, this ID will be theIPv4 address for the PW.

Step 7 Verify that the BGP neighbor is up.

Step 8 If you are using PW in the core, verify that the PWs are properly configured on both PEs.

Step 9 Check that configurations are correct on all peers in the VPLS domain. This includes, for example, loopbacks, IGP (OSPF or ISIS), LDP, BGP, and L2VPN.


Note L2VPN services rely on Layer 3 connectivity from the PE through the core. If you need to reconfigure any routing parameters, use the procedures shown in Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 4.0.



Using show and debug Commands

SUMMARY STEPS

1. debug mpls ldp transport events

2. debug mpls ldp transport connections

3. show mpls forwarding tunnels detail

4. debug mpls ea platform {all | errors | events | info} [ location ]

5. show cef platform trace [adj | all } common | fwdwlk | ipfrr | ipv4 | ipv6 | mpls | rpf | te] location node-id

6. show cef platform resource location node-id

7. show mpls forwarding labels label-id hardware egress location node-id

8. show mpls ldp discovery

9. show mpls ldp neighbor

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

debug mpls ldp transport event

Displays and logs discovery and connection setup/shutdown events.

Step 2 

debug mpls ldp transport connection

Displays and logs connection setup/shutdown events.

Step 3 

show mpls forwarding tunnels detail

Display MPLS tunnel status.

Step 4 

debug mpls ea platform {all | errors | events | info} [location]

Displays and logs MPLS setup events and errors.

Step 5 

show cef platform trace [adj | all | common | fwdwlk | ipfrr | ipv4 | ipv6 | mpls | rpf | te] location node-id

Display data path setup event and error logs.

Step 6 

show cef platform resource location node-id

Display line card resource event and error logs.

Step 7 

show mpls forwarding label label-id hardware egress location node-id

Display MPLS label status.

Step 8 

show mpls ldp discovery

Display MPLS LDP status.

Step 9 

show mpls ldp neighbor

Display MPLS LDP neighbor status.

IP Packets Not Forwarded to LSP

These commands help to troubleshoot IP packets not being forwarded on the label switched path (LSP).


Step 1 Check the prefix information.

RP/0/RSP0/CPU0:router# show cef prefix/length
 
   

Step 2 Check the hardware label FIB.

RP/0/RSP0/CPU0:router# show mpls forwarding labels label-id hardware egress location 
node-id
 
   

Step 3 Find out whether the ARP resolves for the next hop prefix.

RP/0/RSP0/CPU0:router# show arp prefix location node-id
 
   

Workaround

If ARP is not resolved, ping the destination and run the show arp command again to see if the ARP resolves. If it does not resolve, it means there is no path to reach the destination, or the destination is not operational.

If ARP is resolved, use the clear arp location node-id command to clear the ARP information on the node. This command clears the current ARP table entries, and the system will refill the ARP entries with the latest ARP information. This might help if there are stale and incorrect entries in the ARP table.

IP Packets Not Forwarded to MPLS TE Tunnel


Step 1 Check the tunnel adjacency of the prefix.

RP/0/RSP0/CPU0:router# show cef prefix hardware ingress location node-id
 
   

Step 2 Ensure that the MPLS traffic tunnel is up.

RP/0/RSP0/CPU0:router# show mpls traffic-eng tunnels up
 
   

Step 3 Check the hardware TE label FIB by running the following command on the ingress LC for the unicast traffic.

RP/0/RSP0/CPU0:router# show cef adjacency tunnel-te tunnel-id hardware ingress location 
node-id
 
   

Workaround:

Enter the shut command (followed by commit) and the no shut command (followed by commit) on the tunnel interface to reprogram the hardware.

MPLS Packets Not Forwarded to MPLS TE Tunnel


Step 1 Ensure that transmit adjacency is complete.

RP/0/RSP0/CPU0:router# show mpls forwarding labels label-id hardware egress location node-id

Step 2 Ensure that hardware tunnel adjacency is complete by running the following command on the ingress LC for the unicast traffic.

RP/0/RSP0/CPU0:router# show cef mpls adjacency tunnel-te te-id hardware egress location node-id


Workaround

Perform the shut command (followed by commit) and the no shut command (followed by commit) of the tunnel interface to reprogram the hardware.

MPLS TE Tunnels Do Not Come Up


Step 1 Ensure that the tunnel egress interface is configured in RSVP.

rsvp
 interface Bundle-Ether1
  bandwidth 100000
 !
 interface GigabitEthernet0/1/0/2
  bandwidth 100000
 !
 interface GigabitEthernet0/4/0/8  <<---- tunnel egress interface
  bandwidth 100000
 !
 interface GigabitEthernet0/4/0/20
  bandwidth 100000
 !
mpls traffic-eng <<---- Ensure that the tunnel egress interface is configured in mpls 
traffic-engineering config
 interface Bundle-Ether1
 !
 interface GigabitEthernet0/1/0/2
 !
 interface GigabitEthernet0/4/0/8 <<---- tunnel egress interface
 !
 interface GigabitEthernet0/4/0/20
 !
 
   

Step 2 Verify that the tunnel egress interface is up, for example:

RP/0/RSP0/CPU0:router# show interface GigabitEthernet0/4/0/8

Step 3 Ensure that traffic engineering is configured in OSPF.

router ospf te
 log adjacency changes detail
 router-id 192.168.1.30
 area 0
  mpls traffic-eng
 
   

Step 4 Ensure that ping is successful on tunnel destination IP.


FRR-Protected Tunnel Goes Down After Triggering FRR

Fast ReRoute (FRR) is a mechanism for protecting MPLS Traffic Engineering (TE) label-switched paths (LSPs) from link and node failures by locally repairing the LSPs at the point of failure, allowing data to continue to flow on them while their headend routers attempt to establish new end-to-end LSPs to replace them. FRR locally repairs the protected LSPs by rerouting them over backup tunnels that bypass failed links or nodes.


Step 1 Ping the address in an updated sender template.

RP/0/RSP0/CPU0:router# ping PLR_Address

Step 2 Ensure that the MP address is reachable. Check forwarding over the backup tunnel is working.

RP/0/RSP0/CPU0:router# ping backup_tunnel_destination

Step 3 Ensure that the backup tunnel is in Up, Up state.

RP/0/RSP0/CPU0:router# show mpls traffic-eng tunnels

Step 4 Check RSVP traces to find out why the tunnel went down.

RP/0/RSP0/CPU0:router# show mpls traffic-eng trace event


MPLS TE FRR Database Not Built


Step 1 Ensure that the protected tunnel is fast reroutable.

a. RP/0/RSP0/CPU0:router# show mpls traffic-eng fast-reroute database

Step 2 Ensure that backup does not pass through a protected interface.

RP/0/RSP0/CPU0:router# show mpls traffic-eng tunnel backup protected-interface

Step 3 Ensure that backup has enough backup bandwidth (if configured).

RP/0/RSP0/CPU0:router# show mpls traffic-eng tunnels backup

Step 4 Ensure that backup and protected tunnels have a merge point (check hop information).

RP/0/RSP0/CPU0:router# show mpls traffic-eng tunnels

Step 5 Ensure that protected and backup tunnels are in Up, Up state.

RP/0/RSP0/CPU0:router# show mpls traffic-eng tunnels brief


Note Protected tunnels with 0 signaled bandwidth cannot be protected by limited backup-bw tunnels.


Step 6 Enable debugs, remove, and reapply backup tunnel-te.

RP/0/RSP0/CPU0:router# debug mpls traffic-eng frr

Step 7 Shut and no shut the backup tunnel and/or protected tunnel (if possible). This resets backup tunnel assignments.

Step 8 Ensure that the fast-reroute option is not configured on the backup tunnel.

RP/0/RSP0/CPU0:router# show running-config interface tunnel-te15

Step 9 Find out if backup is assigned to a protected LSP.

a. RP/0/RSP0/CPU0:router# show mpls traffic-eng fast-reroute database

b. RP/0/RSP0/CPU0:router# show mpls traffic-eng forwarding

c. RP/0/RSP0/CPU0:router# show rsvp fast-reroute

Step 10 Ensure that the pool-type of the protected LSP bandwidth and backup-bw of the backup tunnel matches.


MPLS FRR Switch Time Debugging


Step 1 Ensure that the FRR database is built and in ready state.

RP/0/RSP0/CPU0:router# show mpls traffic-eng fast-reroute database

Step 2 Upon FRR triggered, ensure that FRR is in the active state.

RP/0/RSP0/CPU0:router# show mpls traffic-eng fast-reroute database

Step 3 Check FRR switch time of LC that the primary tunnel is failed.

RP/0/RSP0/CPU0:router# show mpls traffic-eng fast-reroute log location node-id

Step 4 Ensure that both primary and backup tunnels on the LC received the FRR trigger.

RP/0/RSP0/CPU0:router# show cef platform trace te all location node-id