Fabric Interconnect local forwarding capability

[m1xed0s]

I have been getting mixed information regarding UCS/HX FI local forwarding capability when FI pair is running in ethernet end-host mode.

I just want to confirm it one last time here:

When UCS FI is running in Ethernet end-host mode, will two VMs (same VLAN 100) running on two different UCS Blades under the same pair of FI (same chassis or different chassis) be able to communicate to each other on layer 2? Assuming the VLAN100 is not trunked between UCS FI and upstream switch (like N5K/N9K or ACI)...

[Wes Austin · Accepted solution]

It depends.

Are those VMs MAC addresses being learned on the same fabric interconnect or is one VM learned on FI-A and one being learned on FI-B?

If both VM MAC address are learned on the same FI, in the same VLAN, they will be switched locally. 

If both VM MAC addresses are learned on different FI (one on FI-A and one on FI-B), even if they are on the same VLAN, the traffic is switched upstream.

I know this is not in scope, but if the VM are in different VLAN, but still learned on the same FI, they STILL need to go upstream to be switched/routed.