If I understand the question correctly, guess you are looking for the mapping details of VM vnic to guest OS ethernet interface. Please let me know if you are looking for any other details.
Sample program to print the Virtual machine network details(Nic name, IPv4, Mac, Nic Key, Portgroup) using vSphere java API. - PrintVMNetworkDetails.java
Output:
Network Adatpter IP4Address Mac Key Portgroup
---------------- ---------- --- --- ---------
Network adapter 1 10.10.10.6 00:15:23:31:c9:22 4000 VM Network
Network adapter 2 10.20.20.7 07:89:61:14:38:66 4001 dvPortgroup
Using the above VM network details it is easy to map the guest OS ethernet number.