Configuring Ms Nlb For Multiple Vm Nics In The Same Subnet; Enabling Uufb; Disabling Uufb For Vms That Use Dynamic Mac Addresses - Cisco Nexus 1000V Troubleshooting Manual

Troubleshooting Microsoft NLB Unicast Mode
S e n d d o c u m e n t c o m m e n t s t o n e x u s 1 k - d o c f e e d b a c k @ c i s c o . c o m .

Configuring MS NLB for Multiple VM NICs in the Same Subnet

When MS NLB VMs have more than one port on the same subnet, a request is flooded, which causes
both ports to receive it. The server cannot manage this situation.
To workaround this situation, enable Unknown Unicast Flood Blocking (UUFB).

Enabling UUFB

To enable UUFB, enter these configuration commands, one on each line. At the end, enter Cntl + Z.
n1000v# configure terminal
n1000v (config)# uufb enable
n1000v (config)#
This configuration conceals the requests from the non-NLB ports and allows the system to function as
it is expected.

Disabling UUFB for VMs that use Dynamic MAC Addresses

Issues might occur for VMs that use dynamic MAC addresses, other than those assigned by VMware.
For ports hosting these types of VMs, disable UUFB. To disable UUFB, enter the following commands:
n1000v(config)# int veth3
n1000v(config-if)# switchport uufb disable
n1000v(config-if)#
Cisco Nexus 1000V Troubleshooting Guide, Release 4.2(1)SV2(2.1)
11-14
Chapter 11 Layer 2 Switching
OL-28795-01