Cisco Nexus 7000 Design Manual page 46

FlexPod Implementation and Design
For more information on Best Practices in Deploying Cisco Nexus 1000V Series Switches on Cisco UCS
B and C Series Cisco UCS Manager Servers, see:
http://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9902/white_paper_c11-558242.html
Cisco Virtual Machine Fabric Extender (VM-FEX)
Cisco Virtual Machine Fabric Extender (VM-FEX) is a technology that addresses both management and
performance concerns in the data center by unifying physical and virtual switch management. The use
of Cisco's VM-FEX collapses both virtual and physical networking into a single infrastructure, reducing
the number of network management points and enabling consistent provisioning, configuration and
management policy within the enterprise. This is achieved by joining the Cisco UCS Manager to the
VMware vCenter management platform via the Cisco UCS vDS VMware plug-in. This integration point
between the physical and virtual domains of the data center allows administrators to efficiently manage
both their virtual and physical network resources. The decision to use VM-FEX is typically driven by
application requirements such as performance and the operational preferences of the IT organization.
The Cisco UCS Virtual Interface Card (VIC) offers each VM a virtual Ethernet interface or vNIC. This
vNIC provides direct access to the Cisco UCS Fabric Interconnects and Cisco Nexus 5500 Series
Switches where forwarding decision can be made for each VM using Cisco VM-FEX interface. Cisco
VM-FEX technology supports two modes of operation:
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•
As shown in
an active virtual interface (VIF) and standby (VIF) defined on the adapter, an adapter that is dual-homed
to Fabric A and B. Combined with the UCS Fabric Failover feature the VM-FEX solution provides fault
tolerance and removes the need for software based HA teaming mechanisms. If the active uplink fails
the vNIC will automatically fail over to the standby uplink and simultaneously update the network via
gratuitous ARP. In this example, the active links are solid and the standby links are dashed. The VM-FEX
dynamic connection policy defines the fabric path preference and convergence behavior allowing system
administrators to fine-tune their approach to resiliency.
VMware vSphere 5.1 on FlexPod with Nexus 7000 Using FCoE
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Emulated mode
The hypervisor emulates a NIC (also referred to as a back-end emulated device) to replicate the
–
hardware it virtualizes for the guest virtual machine. The emulated device presents descriptors,
for read and write, and interrupts to the guest virtual machine just as a real hardware NIC device
would. One such NIC device that VMware ESXi emulates is the vmxnet3 device. The guest OS
in turn instantiates a device driver for the emulated NIC. All the resources of the emulated
devices' host interface are mapped to the address space of the guest OS.
PCIe Pass-Through or VMDirectPath mode
Virtual Interface Card uses PCIe standards-compliant IOMMU technology from Intel and
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VMware's VMDirectPath technology to implement PCIe Pass-Through across the hypervisor
layer and eliminate the associated I/O overhead. The Pass-Through mode can be requested in
the port profile associated with the interface using the "high-performance" attribute.
Figure 21, the path for a single VM is fully redundant across the Cisco fabric. The VM has