Our environment has used an NLB configuration with two NICs for years.  One NIC for the host itself and one for the NLB.  We have also been running the NLB in multicast mode.  Starting with 2008, we began adding the cluster's MAC address as an ARP entry on our layer three switch.  Each server participating in the NLB is on VMware.

Can someone advise what the best procedure is for handling NLB in this day?  Although initial tests with one NIC seem to be working, I do notice that we get a popup warning on the participant servers when launching NLB manager "Running NLB Manager on a system with all networks bound to NLB might not work as expected"... if they are set to run in unicast mode.

With that said, should we not be running multicast?  Will that present problems down the road?

Hi enoobmot11,

You can refer the following KB and the VMware requirement KB:

Network Load Balancing Best practices

https://technet.microsoft.com/en-us/library/cc740265%28v=ws.10%29.aspx?f=255&MSPPError=-2147217396

Multiple network adapters

https://technet.microsoft.com/en-us/library/cc784848(v=ws.10).aspx

The VMware KB:

Microsoft Network Load Balancing Multicast and Unicast operation modes (1006580)

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1006580

Sample Configuration - Network Load Balancing (NLB) Multicast Mode Configuration (1006558)

http://kb.vmware.com/selfservice/search.do?cmd=displayKC&docType=kc&docTypeID=DT_KB_1_1&externalId=1006558

Im glad to be of help to you!