UCS Caveats: Uplinking the VIC

The VIC virtual interface card allows within the UCS universe to dynamically create up to 256 VIF – Virtual Interfaces which dynamically bind to a virtual machine within a major hypervisor (e.g. VMWare vSphere, HyperV should be supported soon).

The VIC therefore is bypassed by the virtual switching layer within the hypervisor and provides a reasonable I/O performance advantage compared to classical virtual switching concepts. Basically a “virtual switch” module within the network framework of the hypervisor binds the pre-generated logical PCI devices to a dedicated driver within the virtual machine.

Given a proper integration the so generated virtual interface shows up within the UCS-Manager running on the Nexus based Interconnect Fabric as a classical switch-port and can be managed by the network staff accordingly.

Reading the details in the white papers, the driver component within the virtual machines supports only a limited number on interfaces, in cases as limited as eleven interfaces on one hypervisor. Due to the adapter pinning that does not only cover the general network interfaces, the number of VIFs grows with the factor of additional uplinks. The biggest number I am aware of right now is 56 interfaces with four uplinks from a FEX module. Given the two interfaces of the adapter card this comes close to the 128 advertised VIFs but you need to run Linux within the VMs and you need that many uplinks.