C-3
Cisco 12000/10700 v3.1.1 Router Manager User Guide
OL-4455-01
Appendix C Investigat ing LSP Black Hol es Using Cisco 1 20 00 Seri es Router Manager Setup
The entry on the P router shows untagged, so label-switched packets for this destination will be sent out
without an y labe ls. Since the VPN lab el was lost, it wi ll nev er be rece i ved b y PE2, and PE2 will not ha ve
the correct information to forward the packet to the proper VPN destination.
This information is the same as that displayed when the follo wing Cisco IOS command is ex ecuted:
show mpls fo rwar ding-t abl e
The outp ut yo u see is as shown i n Table C-1:
Solution
There are se ve ral solutions to this problem, a nd the e asiest is to change the sub-net mask for the loopback
address on PE2 to 255.2 55.255.25 5, from 255.255. 255.0 .
When you d o t his, an d r ef res h th e MPLS Forwardi ng Info rma ti on win dow, or wa it for i t t o ma nu all y
update , you n ow 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 Tunne l Id Switched Interface
12307 Untagged 10.5.5.5/32 365 Gi1/0 10.8.8.5