What is Port-cpp in fdb tables?

[dgsong]

Hi everyone. Sometimes when I look at fdb tables when I can't communicate, it looks like Port-cpp, but after some time it changes to normal interface.

 

what is Port-cpp in fdb tables?

[dgsong]

The failed mac is the mac on the Cisco switch.
The downstream switch is ERS3626GTS and is set to mlt, but the Cisco switch that has failed is connected to ERS.
No Loop failures occurred at that time.
Topology is VSP SW(Core) - ERS SW(Distribute) - Cisco SW(Access).
VSP switches are gateways for ERS switches and Cisco switches.
Multiple Cisco switches are connected to an ERS switch, but only one has been changed from a VSP switch to Port-cpp, making it impossible to communicate.
So I wondered what Port-cpp meant.
Thanks.