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The 2040 only has only so many ports.
A virtual NIC, or VIF, is 802.3ad link aggregation - also refered to as 'ether channel'.
You'd need to configure switch ports to support this.
There's also the concept of VLANs, or 'trunking' port groups that you can implement on virtual or physical interfaces.
You can read the 'Networking Guide' in your Data ONTAP docs for more information.
See also - the 'vif' command and the 'vlan' command.
Also - the 2040 controlers have the remote management ports available for management traffic ...
You mention top/bottom ports. On the 2040 those are seperate controllers.
There is the Installation Guide for the 2040:
https://now.netapp.com/NOW/knowledge/docs/hardware/filer/210-04471+B0.pdf
I hope this response has been helpful to you.
At your service,
Eugene E. Kashpureff
ekashp@kashpureff.org
Fastlane NetApp Instructor and Independent Consultant
http://www.fastlaneus.com/ http://www.linkedin.com/in/eugenekashpureff
(P.S. I appreciate points for helpful or correct answers.)