Load Based Teaming on UCS

[TheVMinator]

I am using Load based teaming on UCS.  If vmnic0 is connected to the physical network through Fabric Interconnect A, and the connection from this fabric interconnect to the physical switch becomes saturated, does the load based teaming algorithm sense that?  Or does it not sense it due to the fact that the vmnic is in reality is not a physical NIC but is actually just a logical representation of a physical NIC?

[MKguy]

LBT basically works at layer 1, on the physical level only. As such it can only base its vNIC/pNIC distribution algorithm on the bandwidth of its own physical link. LBT is completely clueless if a link behind the hosts own physical link is saturated.

[TheVMinator]

Thanks for your reply.  Yes I'm aware that lbt can't sense beyond the hosts physical NIC.  But the question has to do more with whether UCS takes that virtual NIC that it presents and presents it in such a way that LBT can sense the contention the virtual NIC experiences as it contends with other virtual NICs within UCSes own world to place ethernet frames onto the wire.  

[chriswahl]

The short answer is: no.

The hypervisor has no visibility into a Fabric Interconnect's uplink connections. The same principle would hold true if it were any other aggregation switch; the hypervisor only knows about the saturation of the actual network adapters (in your case, vNICs) attached to the server.

[TheVMinator]

OK thanks for the info.  So in this scenario, when - if ever - would the LBT algorithm trigger traffic to change from one vmnic to the other, since it can't see layer 1 at all?