Troubleshooting guide

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ATM and Layer 3 Switch Router Troubleshooting Guide
OL-1969-01
Chapter 8 Troubleshooting Tag and MPLS Switching Connections
Troubleshooting MPLS Connections
The Outgoing tag or VC field displays the label assigned by the next hop, or VPI/VCI used to get to the
next hop.
• [T]—Means forwarding through a TSP tunnel.
• Untagged—Means there is no label for the destination from the next hop, or label switching is not
enabled on the outgoing interface.
• Pop tag—Means that the next hop advertised an implicit NULL label for the destination, and that
this router deleted the top label from the stack.
• Aggregate—Means directly connected VRF routes.
Step 2 Check the Prefix or Tunnel Id field. It should displays the address (Loopback 0 interface IP address) or
tunnel to which packets with this label are going. If it does not, check the interface configuration.
The Bytes tag switched field displays the number of bytes switched with this incoming label.
Step 3 Check the Outgoing interface field. It should display the correct interface configured to the next hop on
either side of the switch router.
Step 4 Check the Next Hop field. It should display the correct IP address to the next hop interface.
Verifying Label Bindings
Follow these steps to verify the label bindings on MPLS interface connections:
Step 1 Verify that labels are assigned to each destination by entering the show mpls ip bindings command.
Other commands such as the show tag-switching forwarding-table {ip address | prefix} detail
command can be used to verify the different routes, and the labels associated with the routes.
8540-P# show mpls ip bindings
4.4.4.0/24
in label: imp-null
out label: imp-null lsr: 111.0.1.18:0
6.6.6.0/24
in label: imp-null
out label: imp-null lsr: 111.0.1.18:0
11.0.0.0/8
in label: 17
12.0.0.0/8
out label: 16 lsr: 111.0.1.18:0
100.1.0.0/16
in label: 16
111.0.1.0/30
in label: imp-null
out label: imp-null lsr: 222.2.1.1:0
out label: 20 lsr: 111.0.1.18:0
111.0.1.16/30
in label: imp-null
out label: 16 lsr: 222.2.1.1:0
out label: imp-null lsr: 111.0.1.18:0
171.69.0.0/16
out label: imp-null lsr: 111.0.1.18:0
171.69.1.0/24
in label: imp-null
out label: imp-null lsr: 222.2.1.1:0