Software version and topology description (see topology below):
1. As shown in the topology in the attachment below, the attachment contains the configuration file of the P device (P-configuration.txt). In the topology, Cisco7206 15.2(4)M11 version software is used to run BGP MPLS L3VPN (the public network tunnel protocol is LDP);
2. IP address 4.4.4.4 on CE1 and IP address 5.5.5.5 on CE2 can communicate with each other normally through MPLS L3VPN;
3. Enable NetFlow collection (inbound and outbound) on the g1/0 interface of the P device, enable NetFlow V9 and export NetFlow packets to PC3;
4. Refer to the official manual to enable the MPLS-aware NetFlow feature, that is, configure ip flow-cache mpls label-positions 1 2;
5. Continue to send traffic with the source IP address 4.4.4.4 and the destination IP address 5.5.5.5 on CE1.
Problem and fault description (see Flow1 with red color below) :
Capturing NetFlow packets on the links on P and PC3, we found that the Flow record of 5.5.5.5 contains public network LDP and VPN MPLS labels (200/304), but the MPLS TopLabelType and TopLabelAddr fields are invalid and are 0 and 0 respectively. 0.0.0.0. The label type and IP address at the top of the MPLS stack cannot be viewed through the show ip cache verbose flow command.
Topology:
