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Cisco 12000/10700 v3.1.1 Router Manager User Guide
OL-4455-01
Appendix C Investigating LSP Black Holes Using Cisco 12000 Series Router Manager
Setup
The entry on the P router shows untagged, so label-switched packets for this destination will be sent out
without any labels. Since the VPN label was lost, it will never be received by PE2, and PE2 will not have
the correct information to forward the packet to the proper VPN destination.
This information is the same as that displayed when the following Cisco IOS command is executed:
show mpls forwarding-table
The output you see is as shown in Table C-1:
Solution
There are several solutions to this problem, and the easiest is to change the sub-net mask for the loopback
address on PE2 to 255.255.255.255, from 255.255.255.0.
When you do this, and refresh the MPLS Forwarding Information window, or wait for it to manually
update, you now see:
Figure C-3 Example MPLS Forwarding Information Window
Table C-1 Example Output
Local Outgoing Prefix Bytes Tag Outgoing Next Hop
tag tag or VC or Tunnel Id Switched Interface
12307 Untagged 10.5.5.5/32 365 Gi1/0 10.8.8.5