Information from internet: https://forums.juniper.net/t5/vMX/vMX-max-interface/td-p/293775
ESXi has the limitation of 10 Virtual NICs per VM, which limits the number of revenue interface to 8. (1 is used for management and 1 is used for vfp-vcp inter-connection)
https://www.vmware.com/pdf/vsphere5/r55/vsphere-55-configuration-maximums.pdf, Page 2: Virtual NICs per virtual machine 10
I try to add more but it seems this is maximum, 8 interfaces. Other 2 are for internal communications. One is connected between RE and PFE and an other is for technical communication of engineers devices.
Active Virtual NICs when vMX RE and v MX PFE are power-on!