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
224.0.0.0/4 drop
224.0.0.0/24 receive
255.255.255.255/32 receive
The information displayed by entering the show ip cef command is built from the IP routing table, and
resides on the route processor.
The following is an explanation of the information in the Next Hop column:
• Attached—This is a directly connected interface subnet. For example, 10.85.40.0/24 is the IP subnet
assigned to interface Fast Ethernet1/0/15 with a 24-bit mask.
• Received—These entries are ARP entries for the directly connected interfaces. You will see three
entries here for each directly connected interface. For example, prefix 10.85.40.254/32 is the IP
address for interface Fast Ethernet 1/0/15. Prefix 10.85.40.0/32, using IP conventions means that
this specific interface, combined with prefix 10.85.40.255/32, is the broadcast address.
• xxxx.yyyy.zzzz.aaaa—These IP addresses belong to either the end station connected to the interface
(ARP entries), or to the next-hop router for a specific subnet. For example, prefix 111.0.1.1/32 is the
address of the provider edge switch router. The prefix entry and next-hop entry are the same. Prefix
entry 222.2.1.1/32 is a route learned via next-hop 111.0.1.1.
Verifying MPLS
Follow these steps to verify the MPLS interface connections:
Step 1 Verify that a label distribution protocol is running on the requested interfaces, using the show mpls
interfaces command.
8540-P# show mpls interfaces
Interface IP Tunnel Operational
FastEthernet11/0/0 Yes (tdp) No Yes
FastEthernet11/0/1 Yes (tdp) No Yes
FastEthernet11/0/4 Yes No No
FastEthernet11/0/5 Yes No No
Step 2 Verify the contents of the following fields:
• IP Field—Shows that MPLS IP is configured for an interface. The label distribution protocol (LDP)
appears in parenthesis to the right of the IP status. The LDP is either TDP, defined in the Cisco Tag
Switching architecture, or LDP, as defined by IETF in RFC 3036.
• Tunnel Field—Indicates the traffic-engineered capacity on the interface.
• Operational Field—Shows the status of the LDP.