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
Troubleshooting MPLS Connections
This section describes troubleshooting MPLS connections, and uses an OSPF sample configuration.
Before you start troubleshooting the MPLS connection, confirm that you have configured the following:
• An IP address, and a routing protocol such as Open Shortest Path First (OSPF) or Intermediate
System-to-Intermediate System (IS-IS).
• Cisco Express Forwarding (CEF) or distributed CEF switching on all routers and ATM switch
routers.
• General Multiprotocol Label Switching (MPLS) or tag switching on all routers and ATM switch
routers.
• MPLS or tag switching on all required interfaces.
Troubleshooting MPLS interface connections is described in the following sections:
• Verifying CEF Switching, page 8-20
• Verifying MPLS, page 8-23
• Pinging Neighbors, page 8-24
• Verifying Label Distribution, page 8-24
• Verifying Label Bindings, page 8-25
• Troubleshooting MPLS VPN, page 8-26
To troubleshoot MPLS interface configurations, use the following commands:
Figure 8-5 shows a customer VPN connection over an MPLS Fast Ethernet backbone connection.
Command Purpose
show ip protocols Shows the parameters and current state of the active routing
protocol process.
show ip route Shows the current state of the routing table.
show ip cef [summary] Shows the entries in the Forwarding Information Base
(FIB) table based on the IP address, to verify that CEF has
the correct precedence value for the prefix.
show mpls interfaces Shows the MPLS forwarding information.
show mpls ip binding Shows the MPLS IP Label Information Base (LIB) table.
traceroute Used to discover the routes that packets actually take when
traveling to their destination
show mpls forwarding-table Shows the MPLS Forwarding Information Base (FIB)
table.